ROAD SAFETY AUDIT AND
A CASE STUDY ON KANO-KADUNA ROAD IN NIGERIA
A THESIS SUBMITTED TO
THE GRADUATE SCHOOL OF NATURAL AND APPLIED SCIENCES
OF
ATILIM UNIVERSITY
BY
NURA BALA
IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE
DEGREE OF
MASTER OF SCIENCE
IN
THE DEPARTMENT OF CIVIL ENGINEERING
MARCH 2014
Approval of the Graduate School of Natural and Applied Sciences, Atılım
University.
_____________________
Prof. Dr. Ibrahim AKMAN
Director
I certify that this thesis satisfies all the requirements as a thesis for the degree of
Master of Science.
_____________________
Assoc. Prof Dr. Tolga AKIŞ
Head of Department
This is to certify that we have read the thesis “Road Safety Audit and A case Study
on Kano-Kaduna Road in Nigeria” submitted by “Nura Bala” and that in our opinion
it is fully adequate, in scope and quality, as a thesis for the degree of Master of
Science.
.
_____________________
Asst. Prof. Cumhur AYDIN
Supervisor
Examining Committee Members
Assist. Prof.Dr. Cumhur Aydin
_____________________
Assoc. Prof.Dr Hediye Tuydes
_____________________
Dr. Meriç Gokdalay
_____________________
26 March 2014
I declare and guarantee that all data, knowledge and information in this document
has been obtained, processed and presented in accordance with academic rules and
ethical conduct. Based on these rules and conduct, I have fully cited and referenced
all material and results that are not original to this work.
Nura Bala:
ABSTRACT
ROAD SAFETY AUDIT AND
A CASE STUDY ON KANO-KADUNA ROAD IN NIGERIA
Nura Bala
M.S., Civil Engineering Department
Supervisor: Asst.Prof.Dr. Cumhur Aydin
March 2014, 102 pages
The consequence of increasing number of traffic volume, road safety improvement is
becoming a major policy for the road authorities. Road accidents create both social and
economic cost on the country’s economy. When this is taken into consideration, it is
therefore important to display different solution alternatives considering the budget
limitations of the road authorities.
Road accidents are serious problems throughout the world especially in low and middle
income countries considering social, health and economic terms. The number of road
accidents in such countries tends to increase every year.
In this thesis, a case study is selected in Nigeria and the studies were performed to
summarize actual practices of road safety auditing on existing roads in different
countries. By taking account these different opinions and auditing procedures into
account a strategy for road safety auditing on existing roads that fits to Nigerian roads
conditions is proposed.
For an evaluation, a case study was conducted in order to determine whether the
proposed methodology adds a value to the highway network follow up and
improvements. Based on this study, the audit report was prepared to summarize findings
with possible countermeasures.
Keywords: Road Safety, Road Safety Audit
i
ÖZ
KARAYOLU GÜVENLİĞİ ETÜDÜ:
KANO- KADUNA KARAYOLUNDA BİR ÖRNEK ÇALIŞMA
Nura Bala
Yüksek Lisans, İnşaat Mühendisliği Bölümü
Danışman: Y. Doç. Dr. Cumhur Aydın
Mart 2014,102 sayfa
Trafik hacimlerinin artması sonucu, karayolu güvenliği iyileştirmesi karayolu ile ilgili
kuruluşların temel politikası olmaktadır. Yol kazaları ülke ekonomisine hem sosyal hem
de ekonmomik maliyetler yaratmaktadır. Bu husus dikkate alındığında, karayolu
otoritelerinin bütçe kısıtlarını referans alan değişik çözüm alternatiflerinin ortaya
konması önemlidir.
Karayolu trafik kazaları bütün dünyada ancak özellikle düşük ve orta gelirli ülkelerde
sosyal, sağlık ve ekonomik açıdan çok endişe verici durumdadır. Bu tür ülkelerde yol
kazaları ayrıca her yıl artma eğilimindedir.
Bu tezde, değişik ülkelerde trafiğe açık karayollarında uygulanan ‘karayolu güvenlik
etütleri’ incelenerek, Nijerya’da bir örnek çalışma gerçekleştirilmiştir. Ayrıca bu
analizler ve örnek çalışma dikkate alınarak Nijerya’da trafiğe açık karayollarında
uygulanabilecek bir ‘karayolu güvenlik etüdü’ staratejisi önerilmiştir.
Değerlendirmede, önerilen metodolojinin karayolu ağı izlenmesi ve iyileştirmeye bir
katkı verip veremeyeceği örnek çalışma kapsamında incelenmiştir. Bu çalışmayı baz
alarak, yol güvenliğini tehdit eden bulgular ve uygulanması mümkün iyileştirme
önerilerinin yer aldığı bir etüt raporu hazırlanmıştır.
Anahtar kelimeler: Karayolu güvenliği, Karayolu Güvenliği Etüdü
ii
DEDICATION
This thesis is dedicated to all of the mentors that I have had in my life especially Alhaji
Rufa’i Buhari (Yaya Ma’aji) for his endless care and support. My mother for her
optimistic view of life and never letting me give up. My father for showing me how to
always conduct myself honestly and also for guiding me into civil engineering. My
lovely wife for her unconditional love and support. My brothers for providing me with a
rock solid base from which to go after my dreams. My all friends and teachers I have
had in my life, they have always shown me love and encouragement.
Finally to Kano state and the executive governor Engr Dr Rabi’u Musa kwankwaso for
sponsoring my masters study in Atilim University Turkey.
iii
ACKNOWLEDGMENTS
My profound gratitude goes to my able supervisor Asst.Prof.Dr. Cumhur Aydin for his
guidance and insight throughout the research.
I am very grateful to my parent for their endless support throughout my academic years
and my life in general. Also my appreciation goes to the rest of my family members for
their encouragement and contributions.
My profound gratitude goes to all my friends who have always been source of strength
and encouragement throughout this research.
iv
TABLE OF CONTENTS
TABLE OF CONTENTS ................................................................................................... v
LIST OF TABLES ............................................................................................................. x
LIST OF FIGURES ..........................................................................................................xi
LIST OF ABBREVIATIONS ........................................................................................ xiii
1 INTRODUCTION .......................................................................................................... 1
1.2 Statement of the Problem and Need for the Study in Nigeria .................................. 3
1.3 Importance of Road Safety Audit ............................................................................. 4
1.4 Importance of Road Safety Inspection ..................................................................... 4
1.5 Costs and benefits of Road Safety Audit .................................................................. 4
1.6 Actions for Improving Road Safety on Highways ................................................... 6
1.7 Thesis Scope ............................................................................................................. 7
1.8 Objectives of Road Safety Audit .............................................................................. 7
2 ROAD SAFETY ENGINEERING AND WORLD WIDE EXPERIENCES OF ROAD
SAFETY AUDIT AND ROAD SAFETY INSPECTION ................................................. 9
2.2 Hazardous Roadway Conditions ............................................................................ 11
2.2.1 Roadway Departure Hazards ........................................................................... 11
v
2.2.2 Road Surface Condition ................................................................................... 12
2.2.3 Narrow Roadway and Bridges ......................................................................... 12
2.2.4 Rail Road Crossing .......................................................................................... 12
2.2.5 Work zones ...................................................................................................... 12
2.2.6 Intersections ..................................................................................................... 12
2.2.7 Roadway Design Limitations........................................................................... 13
2.2.8 Roadway Access Problems .............................................................................. 13
2.2.9 Pedestrians and Bicycle Traffic ....................................................................... 13
2.3 How to Approach Road Safety Evaluation ............................................................ 13
2.4 Counter Measure Follow-Up .................................................................................. 14
2.4.1 The Short Term Follow-Up ............................................................................. 15
2.4.2 The Long-Term Follow-Up ............................................................................. 15
2.5 Planning Highway Network for Safety .................................................................. 15
2.6 Road Safety Audit History ..................................................................................... 17
2.7 Definition and Principles of RSA and RSI ............................................................. 18
2.8 Steps of Road Safety Audit .................................................................................... 19
2.9 Stages for Conducting a Road Safety Audit ........................................................... 22
2.10 Review of Existing Practices Regarding Road Safety Inspection in Different .... 23
2.10.1 United Kingdom ............................................................................................ 25
2.10.2 Austria............................................................................................................ 26
vi
2.10.3 Italy ................................................................................................................ 26
2.10.4 France............................................................................................................. 27
2.10.5 Australia and New Zealand............................................................................ 27
2.10.6 Norway........................................................................................................... 27
2.10.7 Kenya ............................................................................................................. 28
2.10.8 Benin Republic .............................................................................................. 28
2.10.9 Tanzania ......................................................................................................... 28
3 METHODOLOGY AND EXPLANATIONS OF ROAD SAFETY AUDIT ............. 30
3.1 Introduction ............................................................................................................ 30
3.2 Methodology for Safety Auditing on Existing Roads ............................................ 30
3.3 General Project Data Required for Road Safety Audit on Existing Road .............. 31
3.3.1 Functional Classification of the Road .............................................................. 31
3.3.2 Traffic Data ...................................................................................................... 33
3.3.4 Speed Data ....................................................................................................... 34
3.3.5 Accident Data .................................................................................................. 35
3.3.6 Safety Audit Checklist on Existing Road ........................................................ 36
A-Road Design Hazards ................................................................................................... 37
3.4 Roadside Safety ...................................................................................................... 38
3.4.1 Safety Zone ...................................................................................................... 38
3.5 Basic Explanations of Typical Hazards .................................................................. 40
vii
3.6 Typical Hazards Countermeasure Selection ........................................................... 47
3.7 Safety auditing reporting ........................................................................................ 53
3.8 Safety Audit Discussions........................................................................................ 53
3.9 Evaluation of Improvement Projects ...................................................................... 53
4 ANALYSIS AND CASE STUDY PRESENTATIONS ............................................... 55
4.1 General ................................................................................................................... 55
4.2 Preconditions .......................................................................................................... 56
4.2.1 General Project Data............................................................................................ 56
4.2.2 Surroundings/Land Use ................................................................................... 58
4.3. Methodology ......................................................................................................... 59
4.5 Observations Performed During Audit ................................................................... 60
4.4 Hazard List ............................................................................................................. 61
4.6 Comparison with the Standard ............................................................................... 62
4.7 Safety Audit Checklist of Existing Road................................................................ 63
4.8 Typical Hazards ...................................................................................................... 70
4.9 Proposal of Countermeasures ................................................................................. 80
4.10 Case Study Conclusıons ....................................................................................... 83
5 CONCLUSIONS AND RECOMENDATIONS ........................................................... 86
5.1 Conclusions ............................................................................................................ 86
5.2 Recommendations .................................................................................................. 87
viii
REFERENCES................................................................................................................. 88
APPENDIX ...................................................................................................................... 91
ix
LIST OF TABLES
Table 1.1 Predicted Road Traffic Fatalities (2)………………………………………….……..2
Table 3.1 Road Safety Audit Checklist……………………………………………………..…36
Table 3.2 Hazard List…………………………………………………………………………..37
Table 3.3 Recommended Clear Zone Width (16)…………………………………………..….40
Table 4.1 Accident Data of Nigeria (3)………………………………………………….…..…56
Table 4.2 Accident Data foe Kano-Kaduna Highway………………………………………….56
Table 4.3 Towns Located Along the Audit Road………………………………………………58
Table 4.4 Hazard Types……………………………………………………………………...…60
Table 4.5 Comparison with AASHTO Standard…………………………………..…………...62
Table 4.6 Safety Audit Checklist for Kano-Kaduna Direction…………………….………..….63
Table 4.7 Safety Audit Checklist for Kaduna-Kano Direction…………………….………..….68
Table 4.8 Most Common and Dangerous Hazards……………………………………………..84
x
LIST OF FIGURES
Figure 1.1 Road Death by Level of Income (1)…………………………………………...1
Figure 1.2 Number of Deaths per year (million) Without Action…………………………2
Figure 2.1 Accident Contributing Factors (12).…………………………………………..10
Figure 2.2 Ideal Roadway Hierarchies……………………………………………………16
Figure 2.3 Road Safety Audit Process (10)……………………………………………….20
Figure 2.4 Current Use of Road Safety Audit in Europe (12)……………………………24
Figure 2.5 Current Use of Road Safety Inspection in Europe (12)……………………….24
Figure 2.6 Current Use of Road Safety Audit in United States (13)……………………,..25
Figure 3.1 Illustration of Access-Mobility Relationship………………………………….33
Figure 3.2 Road Side Safety Design………………………………………………………39
Figure 3.3 Typical Median with Concrete Barrier……………………………………...…43
Figure 4.1 Map of Nigeria Showing Three major Highways (1)……………………….....54
Figure 4.1 Map of Nigeria Showing Three major Highways (1)……………………..…...54
Figure 4.2 Map Showing Kano-Kaduna Highway ..………………………………………55
Figure 4.3 Dangerous Electric Pole Close to the Road Km 47+200. .…………………….70
Figure 4.4 Dangerous Trees within the Safety Zone Area Km 13+100...…………………71
Figure 4.5 Warn out Sign Km 5+300……….……………………………………………..71
Figure 4.6 Improper Connection to gas Station Km 3+400…………..…………………...72
Figure 4.7 Improper pedestrian Crossing Km 5+200…….………………………………..73
Figure 4.8 Missing Shoulder Km 44+100…………………………………………………74
Figure 4.9 Dangerous Fill Slope Km 2+700………….…………………………………...74
xi
Figure 4.10 Dangerous Guardrail Section Km 21+50........................……………………….75
Figure 4.11 Dangerous Potholes on the Pavement Km 9+000 ………..………………….....76
Figure 4.12 Improper Placement of Vertical Sign within the Safety Zone Km 6+400… ......76
Figure 4.13 Dangerous Trees within Safety Zone Km 3+200 ….…………….…………......77
Figure 4.14 Dangerous Support for Vertical Sign Km 43+200 ………………………..…...78
Figure 4.15 Dangerous Road Narrowing Km 0+300 ……………………………………….78
Figure 4.16 Missing Safety Zone Km 5+900..………………………………………..……...79
xii
LIST OF ABBREVIATIONS
AADT
- Average Annual Daily Traffic
AASHTO
- American Association of Highway and Transport
Officials
ADT
AUSTROADS
- Average Daily Traffic
- Association of Australian and New Zealand Road
Transport and Traffic Authorities
ETSC
- European Transport Safety Council
FRSCN
- Federal Road Safety Corps of Nigeria
NHCRF
- National Cooperative Highway Research Program
PIARC
- Permanent International Association of Road
Congresses
RSA
- Road Safety Audit
RSIA
- Road Safety Impact Assessment
RSI
- Road Safety Inspection
TERN
- Trans European Road Network
UK
- United Kingdom
WHO
- World Health Organization
xiii
CHAPTER ONE
1 INTRODUCTION
1.1 General
Road traffic accidents deaths and injuries occur worldwide. It was estimated that over
1.2 million people died each year on the world roads as a result of road traffic accidents.
According to a survey by WHO, more than 3,200 people get killed and over 130 000
injured in traffic every day around the world. Also almost half of all fatal accidents
involve pedestrians, cyclists and power two wheelers, collectively called vulnerable road
users. (1)
Figure 1.1 Road deaths by level of income. (1)
From figure 1.0 above, it can be observed that more than 85% of accident fatalities occur
in low and middle income countries such as Nigeria. Though road fatality rate in high
income countries has been decreasing over the last decades, even in these countries road
accidents remain one the main causes of death, injury and disability.
1
Table 1.1 Predicted Road Traffic Fatalities (2)
REGION
South Asia
East Asia & Pacific
Sub-Saharan Africa
Middle East & North Africa
Latin America & Caribbean
Europe & Central Asia
Sub Total
High income countries
Global total
% CHANGE 2000-2020
144
80
80
68
48
18
83
-28
66
From Table 1.1 above, unless there is concerted action, the global road fatalities is
expected to increase by more than 65% between year 2000 and 2020, with different
trends across the different regions of the world. Fatalities are predicted to be increased
by more than 80% in low and middle income countries, but be decreased by nearly 30%
in high income countries, thus revealing a widening gap between the road safety in rich
and the road safety poor countries.(4)
Figure 1.2 Number of road deaths per year (million) without action. (1)
From figure 1.2 above it is observed that while in many high income countries road
fatality rate have stabilized or decreased, but on the other hands in the majority regions
of the world such as Africa the number of people killed in road traffic accidents is
constantly increasing and If the current trends allowed to continue, traffic accident
related deaths may take the fifth place in the list of death causing, health disorders and
injuries by the year 2030 and results in an estimated 2.4 million fatalities per year. (1)
2
1.2 Statement of the Problem and Need for the Study in Nigeria
Road traffic accident occurs worldwide, but the incidence is more in developing
countries such as Nigeria. The problem of road accidents in Nigeria has reached such an
alarming proportion in such a way that our highways have been converted into dead
zones, killing citizens daily. According to FRSCN 7,269 peoples died, 20,752 persons
sustained various degrees of injuries and 7,517 people are left permanently disabled in
the year 2012 as a result of road traffic accidents across highways in Nigeria. (3)
Sudden deaths due to road fatal accidents have continued to be source of grief in a
number of homes in Nigeria. There is scarcely a week that passes without an account of
a ghastly road traffic accident with many deaths being recorded. Despite the annual road
safety campaigns, mobilization of FRSCN, warning against reckless driving and road
marshals on our roads, it is unfortunate that the number of traffic accidents is always on
increase leading to loss in both human and material resources through road traffic
accidents.
Deaths as a result of motor vehicle accidents constitute a great economic loss to our
society. Accidents have far reaching effects on families’ life, on development and
economic life of the country. The strained health services in the country often cannot
adequately look after accident victims and there by entire families, relations, friends and
collogues were suddenly swept away, which brings grief and economic hardship to the
families and survivors.
Besides those that died in road traffic accidents there are many others who survived with
residual disabilities of varying degrees of severity, who ends up as burden to the society.
The country itself suffers by losing its talented and productive manpower often in the
prime of life.
Road traffic accidents have physical, social, emotional and economic implications. The
global economic cost of road traffic accidents was estimated at $518 billion per year in
2003 with $100 billion of that occurring in poor developing countries such as Nigeria.
(2)
Nigeria loses about 80 billion Naira (4.9 billion US $) annually to road traffic accidents.
Of all subjects that are involved in road traffic accidents in Nigeria, 29.1 per cent suffer
disability and 13.5 per cent are unable to return to work. (3)
From all search carried out for the preparation of this thesis there was no any relevant
report regarding highway safety audit in Nigeria, therefore it can be stated that road
safety audit is a new practice in Nigeria, it was never carried out before and in order to
3
save life’s it is very important to introduce and carry out a road safety audit on Nigerian
highways in order to reduce the number of persons died and severity of injuries on the
roads annually.
1.3 Importance of Road Safety Audit
Road safety auditing is a recognized crash prevention road safety tool worldwide that
has the following importance:
a) A reduction in the likelihood of crashes on the road network,
b) A reduction in the severity of crashes on the road network,
c) An increased awareness of safe design practices among traffic engineers and
road designers,
d) A reduction in the need to modify projects after they are built,
e) A reduction in the life-cycle cost of a road,
f) A more uniform road environment that is more easily understood by road users,
g) A better understanding and documentation of road safety engineering,
h) Eventual safety improvements to standards and procedures,
i) More explicit consideration of the safety needs of vulnerable road users. (4)
1.4 Importance of Road Safety Inspection
The main importance of road safety inspection in general can be summarized as follows:
a) To identify potential road or traffic safety concerns for all road users,
b) To minimize the risk and severity of road accidents that may result from the
existing
situation of a road section,
c) To minimize unsustainable losses to health and economy. (5)
1.5 Costs and benefits of Road Safety Audit
The costs of RSA can vary greatly depending on the size of the project and the phase in
which the audit takes place. But the main immediate benefits of road safety audit will be
accident savings.
However, there are other longer terms and more broadly based potential benefits, these
include not just the immediate accident savings on the schemes subjected to the
procedures, but more generally, improvements to the management of design and
construction, reduced whole-life cost of road schemes, the development of good safety
engineering practice, the explicit recognition of the safety needs of road users, and the
improvement of design standards for safety.
4
The benefits of an RSA are mainly the costs saved on crashes that have been prevented
by following the audit's recommendations. In addition, Gadd mentions a series of
qualitative benefits after completion a diminished risk of crashes and the repair works
resulting from them, a reduction of the total project costs, a greater awareness of road
safety and quality in design processes, better facilities for vulnerable road users, and a
contribution towards achieving road safety targets, better standards, and design
guidelines. (6)
A distinction can be made between direct and indirect costs. The direct costs are the time
spent by auditors and the extra time that designers need to include the recommendations
in the design. Experiences in Denmark estimate the direct costs to be an average of 1%
of the total costs of a project. (6)
A study in Australia by Van Hout and Kemperman reveals that the direct costs vary
between € 600 and € 6,000, an average of only 0.2% of the total project costs. Also
according to Van Schagen the direct costs during the trial audits in the Netherlands were
between € 3,200 and € 4,600; at the present price level this would be between € 4,300
and € 6,600. The earlier in the process an initial RSA is carried out, the lower the
relative costs in proportion to the total costs. (6)
The indirect costs are the extra costs of construction and reconstruction activities that
result from the auditors’ recommendations. Estimates based on international experiences
are between 1% and 2% of the total project costs. In smaller projects the direct and
indirect costs of an RSA are relatively higher than in large projects. (6)
A study in Denmark focused on 13 projects that had undergone an RSA. The number of
crashes if no RSA had taken place was estimated. The savings on crash costs resulted in
a cost-benefit ratio of 1:1.46. (7)
Another study in Jordan focused on projects in which no RSA had taken place and
where road safety problems occurred a short time after the projects had been completed.
The study assumed that the repair works that were necessary after the crashes occurred
would have been included in the initial design if an RSA had been carried out. The
number of crashes that could have been prevented was estimated, resulting in a cost
benefit ratio of 1:1.2. (7)
Also a Surrey County Council in 1994 compared 38 reconstruction plans half of which
had been subjected to an RSA and the other half had not. The annual average numbers of
casualties saved declined by 1.25, from 2.08 to 0.83 on the reconstructed roads where an
RSA had been carried out. On roads where no RSA had been carried out, the annual
average number of casualties declined by 0.26, from 2.60 to 2.34. (7)
5
However, it is by no means clear if the large decline on roads where an RSA was carried
out was exclusively attributable to the RSA, the reconstruction activities on roads with
an RSA and those on roads without an RSA were not really comparable.
Another study that is being carried out in Great Britain compared before and after crash
statistics for a sample of audited schemes and non audited schemes, the study found that
audited schemes achieved an average casualty saving per year of 1.25, compared to a
saving of 0.26 for non-audited schemes. (6)
From the above studies carried out in different parts of the world by different road safety
auditors it can be seen that road safety audit is a very essential tool to be employed in
order to reduce the cost and number of traffic accidents globally.
1.6 Actions for Improving Road Safety on Highways
By planning more efforts for increasing highway safety, some transportation agencies
have introduced safety programs specifically designed to study and improve some
important geometric elements contributing to highway accidents.
At the same time, engineering design has greatly been improved in terms of increasing
safety into road structure and environment. In earlier years, engineers designed and built
highways, which provides a minor of protection to vehicles colliding with infrastructure
or roadside elements outside travel lanes. (8)
In 1960s and 1970s, engineers have started to build more “forgiving highways” which
incorporated critical design elements that mitigated the consequence of colliding with
elements beyond the travel lanes. More recently, engineers have begun to develop
“caring highways” by emphasizing the need to prevent (rather than mitigate) collisions.
(8)
Although it is in practiced for nearly two decades, the concept of Road Safety Audits has
only recently gained acceptance in North America. Originally developed in the United
Kingdom in the 1980s as part of Accident Investigation and Prevention techniques, they
have evolved to the point where they are now an integral component of the road safety
process. Road safety audits help to ensure that issues associated with road safety are
specifically addressed and are given equal importance as the other factors in a design
project. (8)
On the other hand, Road Safety Impact Assessment (RSIA) is just come into the Road
Authorities Agendas through the proposed applications and obligations that have been
set by the European Parliament and The Council of The European Union. The Road
Safety Impact Assessment’ means a strategic comparative analysis of the impact of a
6
new road or a substantial modification to the existing network on the safety performance
of the road network. The Commission expressed the need to carry out safety impact
assessments and road safety audits, in order to identify and improve high accident
concentration sections within the Community. It also sets the target of halving the
number of deaths on the roads within the European Union between 2001 and 2010. (9)
The setting up of appropriate procedures is an essential tool for improving the safety of
road infrastructure within the Trans-European Road Network (TERN). Road safety
impact assessments should demonstrate, on a strategic level, the implications on road
safety of different planning alternatives of an infrastructure project and they should play
an important role when routes are being selected. The results of road safety impact
assessments may be set out in a number of documents. Moreover, road safety audits
should identify, in a detailed way, unsafe features of a road infrastructure project. It
therefore makes sense to develop procedures to be followed in those two fields with the
aim of increasing safety of road infrastructures on the trans-European road network. (10)
Establishment and implementation of procedures are required by the directive that is
relating to road safety impact assessments, road safety audits moreover the management
of road network safety and safety inspections by the Member States. Also directive shall
apply to roads which are part of the trans-European road network, whether they are at
the design stage, under construction or in operation. (10)
1.7 Thesis Scope
The scope of this thesis is to carried out a road safety audit in Nigeria and to evaluate
different road safety auditing techniques on the road selected as a case study.
Throughout the implementation and reporting at this case study, the present safety
situation of Nigerian roads and available techniques will be evaluated.
For the purpose of this thesis a 50 km section of Kano-Kaduna express way which is an
existing roadway in Nigeria will be considered as a case study. The road is a dual
carriage way which connects two major cities with high population in Nigeria and also
many towns were located along the road.
The aim of this thesis is to evaluate different road safety auditing techniques and
implement a case study on an existing road section in Nigeria.
1.8 Objectives of Road Safety Audit
The main objective of any road safety audit is to ensure that all new and existing
highway schemes operate as safely as is practicable. This means that safety should be
7
considered throughout the whole preparation, construction and after construction of any
project but more specific objectives are:
a. To help produce designs and roads that reduce the number and severity of
crashes
b. To ensure that road elements with an increased risk potential are removed or that
measures are identified to reduce the risk thereof
c. To Reduce likelihoods of accidents
d. To minimize the severity and crash risk of road traffic crashes that may be
Influenced by the road facility or adjacent environment;
e. To minimize the need for remedial measures after the opening of a new road
Project
f. To identify and report on the crash potential and safety problems of a road
Project
g. To avoid the possibility of the scheme giving rise to accidents elsewhere in the
road network. (11)
The thesis is divided into five chapters as follows:
Chapter 2 provides an international overview on the historical evolution of road safety
audits. This chapter also describes the principles underlying road safety audits. It
provides a synthesis of concepts, stages and implementation of road safety audits. It
presents also the Turkish road safety audit process of existing roads.
Chapter 3 describes the basic structure and explanations of road safety audit on existing
road and it’s reporting
Chapter 4 presents road safety audit on existing which were conducted in Nigeria along
Kano-Kaduna Highway and Proposal of some specific countermeasures about the safety.
Chapter 5 presents conclusion and recommendations.
8
CHAPTER TWO
2 ROAD SAFETY ENGINEERING AND WORLD WIDE EXPERIENCES OF
ROAD SAFETY AUDIT AND ROAD SAFETY INSPECTION
2.1 Road Safety Engineering
Road safety engineering is a branch of traffic engineering that deals with reducing the
frequency and severity of crashes. It uses several aspects such as physics and vehicle
dynamics, as well as road user psychology and human factors engineering, to reduce the
influence of factors that contribute to accident crashes.
Road safety engineering involves the application of road and traffic engineering
principles, based on a sound analysis of all relevant data, with an understanding of road
user behavior in order to identify and implement improvements to bring about cost
effective reductions in crashes and casualties.
Road safety engineering should be applied at all stages of road/transport development
such as in the planning of new developments, in the design of new roads, in safety
improvements for existing roads, in remedial treatments of hazardous locations, and in
routine maintenance programmes.
The three major components of highway safety are driver behavior, vehicle safety, and
roadway safety. Roadway safety refers to that portion of overall highway safety that is
determined by the roadway’s physical features such as road design, roadway signs,
pavement markings, operating conditions, roadside objects (such as utility poles, signs,
trees, guardrails) etc.
To reduce the number of traffic accidents on our roads, we need to understand what
causes the accidents in general. The highway transportation system can be broken down
in to three broad categories:
1- The driver
2- The vehicles
3- The roadway and its environment. (12)
9
Factors that causes accidents usually falls in to one of those categories above and most
accidents have at least one contributing factor and also many accidents have more than
one contributing factor.
A human factor includes things like inattention or distraction of driver, fatigue, use of
alcohol and vision problems. Vehicle factors may be mechanical failures, bad brakes or
tires or any other similar problems and a road related problems can be insufficient sight
distance, poor or missing road signs and changes in roadway width or slippery road
surfaces.
While concentrating on road safety, road design is one of the most important aspects to
be considered regarding highway safety. Roads must be designed to reduce the
unexpected situations, thus reduce the failure in the driver decisions. On the other hand,
traffic control devices also play an important role on the road safety.
We cannot prevent all accidents on our roads but however, a good road safety
improvement plan can be an effective way to reduce the risk of liability. It can reduce
the number of accidents, the loss of lives and the economic costs related to them.
Reducing the number of accidents reduces the exposure to liability and a good safety
planning is a best way to accidents reduction.
Figure 2.1 Accident contributing factors (12)
10
Figure 2.1 above shows that driver errors constitutes the highest percentage among the
three main factors contributing to accidents followed by road condition with the second
and lastly the vehicle defect or malfunction.
Considering road transportation as a system, there are things that we can directly control
and things that we cannot. Drivers and environmental events like weather are hard to
control and If the parts of the system that can be controlled (roads and vehicles) are
designed to allow for those we cannot (road users and weather), the system as a whole
will work better.
The road safety is a complex matter to understand and analyze. Because of this reason, a
model preparation including all of the three elements; human, vehicle and environment
is a very difficult process. These elements can be considered separately or they can be
evaluated together with their relations to each other.
Increase in road safety requirements is an unavoidable consequence of rapid economic
growth. Unless the road safety is maximized, the resultant economic and social costs
could erode a substantial part of the benefits of economic growth. Millions of deaths and
injuries, billions of dollars in medical costs, increased strain in welfare services, loss of
productivity, and poverty problems are some of the consequences of slack road safety.
Recent analysis in Norway and Sweden (Elvik, 1999; Elvik, 2001; Elvik, 2003; Elvik
and Amundsen, 2000) conclude that cost-effective road safety policies could prevent
between 50 and 60% of the current number of road accident fatalities in both countries
(13).
2.2 Hazardous Roadway Conditions
The following below are considered as the hazardous roadway conditions contributing to
accidents regardless of locations on the roadway, these conditions are potentially
dangerous to road users.
2.2.1 Roadway Departure Hazards
Roadway departure crashes occur on both straight and curved sections of roadway and
often involve either rollover of a vehicle or collisions with fixed objects such as trees
and utility poles. Roadside hazards also include steep side slopes, drainage ditches along
the roadway, and narrow shoulders not large enough to accommodate a vehicle in
trouble. (14)
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2.2.2 Road Surface Condition
Some problems in the road surface, such as pavement edge drop-offs, potholes and
reductions in surface friction due to age, wear, inadequate drainage during rain storms,
and incomplete winter maintenance to remove ice or snow obviously impair vehicle
stopping and maneuvering capabilities leading to fatal crashes.
2.2.3 Narrow Roadway and Bridges
A narrow bridge makes it difficult for drivers to safely maneuver in emergency and non
emergency situations because there is simply no enough space to maneuver. Narrow
bridges are particularly hazardous and collisions with bridge ends are relatively
infrequent but they are often severe. Such crashes usually occur when the width of a
bridge is less than that of the approaching traveling lanes and shoulders and as a result
vehicles strike the end of the bridges, guardrails or curbing. (14)
2.2.4 Rail Road Crossing
Rail road crossings is one of the most dangerous places along the roadway sections
because trains cannot stop quickly or steer out of the way and obviously, railroad
crossings are of a critical concern, and they can be incredibly hazardous, regardless of
how busy they are.
2.2.5 Work zones
A Work zones are areas of construction, maintenance, and utility areas, which creates
conditions that can be hazardous to drivers and highway workers. Work zones are a
necessary fact of life in our communities and can cause changes in traffic patterns,
reduced speed limits, causes congestion; and an influx of construction workers and
equipment on the road. Sometimes work zones are poorly marked, and warning signs are
hard to see, especially at night. (14)
Warning signs and traffic control devices may not be related to actual work in progress
or accurately portray real work zone hazards. Drivers thus disregard these warning signs
with potentially tragic consequences.
2.2.6 Intersections
Many intersections are very dangerous intersections, as they are composed with
confusing turn lanes, blind spots, or lack of appropriate or inadequate signage or traffic
12
signals. Obstructions, including vegetation, can block a driver’s view of signs, signals,
and other traffic control devices there by leading to high severity if accident occurs. (14)
2.2.7 Roadway Design Limitations
Many local roads were not built to serve today’s high-volume, high-speed traffic. Their
safety is limited by hazards such as sharp curves, poor signs and pavement markings,
and lack of medians to separate oncoming traffic. These limitations could present an
even greater threat to highway safety because of the expected increase in the car
ownership over years.
Many of these roads are now high speed commuter corridors, because of these their
safety now is compromised by many hazards. Therefore, drivers must therefore be aware
of roadway hazards and drive with extra care. (14)
2.2.8 Roadway Access Problems
Roadway access problems are very familiar problem and also one of the most dangerous
among the hazards. Constantly growing traffic congestion, concerns over traffic safety,
and the ever increasing costs of upgrading our roads have generated a new interest in
managing access to our highway systems. Access management is the process that
provides access to land development while simultaneously preserving the flow of traffic
on surrounding roadways.
Three issues kept in the forefront of access management are safety, capacity, and speed.
Fewer direct accesses, greater separation of driveways, and better driveway design and
location are the basic elements to be considered for safety.
2.2.9 Pedestrians and Bicycle Traffic
Pedestrian and bicycle traffic must be accommodated and speeds must be controlled for
them as they are vulnerable. There were high pedestrian deaths and injuries along the
roads in all over the world and these numbers are expected to increase as our population
increases. Therefore all highways should be design in such a way to accommodate the
safety of pedestrians and bicyclist.
2.3 How to Approach Road Safety Evaluation
Evaluation of completed highway safety projects and programs are essential for safety
professionals to identify the improvements that are working, the ones that are producing
nominal benefit and the ones not working.
13
Road safety programs are prepared and are being applied to reduce the number of
accidents. These programs generally have similar aim which is to reduce the number of
traffic fatalities and injuries.
Once the problem or problems and their sources are identified, then the second step is
the selection of the correct and adequate countermeasures to implement as there is no
single counter measure that is seldom to provide a total solution to a safety problem.
Before finalizing of the treatment decision, all the cost and accident reduction factors of
the different improvement scenarios should be analyzed. The most cost effective
countermeasure has to be applied. The word cost effectiveness generally stands for the
net resource cost of a measure per year of life saved.
The basic methods for solving safety problems can be categorized in to five stages as
follows
1- Identify the type of problem and determine contributing factors
2- Select a countermeasure:
a- Which improvement offers the best results for the least cost?
b- Will a possible improvement solve the problem, or just move it down the road?
c- Will a possible improvement cause problems of its own? If so, are they worse
than the problem you are trying to solve?
3- Install the countermeasure
4- Evaluate success
5- Return to Stage 2 if necessary. (15)
The evaluation of effectiveness of safety projects and programs can lead to continuing
safety improvements at the same level, increasing resource allocations due to success
achieved, or even discontinuing some safety initiatives due to their observed inability to
alleviate traffic crash problems. (5)
2.4 Counter Measure Follow-Up
To understand the effects of countermeasures, it is necessary to follow-up the
application of the different countermeasures after their respective applications. For this
purpose all the data and information that have been recorded before and after (followup) stages of the road section improvements should be saved. Again by that way followup can give the correct and dependable results for the future improvement applications.
Basically there are two methods for counter measure application follow up for different
purposes:
14
2.4.1 The Short Term Follow-Up
Using this method, Short term effects can easily and shortly show if the road users have
taken positive contribution from the improvement and usually takes place immediately
after the application of countermeasure.
2.4.2 The Long-Term Follow-Up
Long term follow-up helps to evaluate if the improvement causes a decrease or an
increase in the danger of accidents at the inspected road. It is usually carried out after
long period of counter measure application.
It is important to start the follow up process just after the implementation of
countermeasures. In this way, it can be possible to observe if the applied countermeasure
is working as it is planned or if it causes another problem which is not predicted before.
It also helps to understand if the countermeasure application totally removes the problem
or it reduces the amount and the severity of the problem.
For estimating the exact results of countermeasures it is necessary to make follow-up for
minimum three years for the long-term evaluations. On the other hand, all changes in the
road and its environment have to be observed, because these changes could affect the
road safety and also affect the countermeasure efficiency.
2.5 Planning Highway Network for Safety
Planning of roads can have a profound effect on the level of road safety, planning road
networks usually contains a complex interaction of land uses and activities. Each type of
land use has its own traffic characteristics and this can lead to safety problems.
15
Mobility
Arterials
Collectors
Access
Locals
Figure 2.2 Ideal roadway hierarchies. (15)
Road hierarchy in highway planning is to consider the functions of local roads,
collectors, and arterials in terms of accessibility and mobility. Local roads mostly
provide access to land, whereas arterials mostly provide mobility for through traffic.
Collectors fall functionally halfway between local roads and arterials as shown in Figure
2.2 above.
Figure 2.2 above indicates that accident and fatality rates on arterial highways with full
control of access are far less than that of collectors and locals with no access control.
The increase in roadside development results in an increase in at grade intersections and
in business with direct access to the highway, this situation always significantly
increases accidents.
Highway network planning for safety should include following three features namely
road hierarchy, land use and access control. Each of the three items above is described
below.
a) Road Hierarchy
1- Highway networks should be clearly categorized into those which are primarily
intended for
mobility and those which are originally designed for access.
2- Unmistakable priority should be indicated at each intersection so that the traffic from
the more important road is always given preference over that from the less important
one. (15)
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b) Land Use
1- Critical observations or careful examination on land development proposals should be
made on traffic and safety implication before approval.
2- Minimizing road traffic and pedestrian conflicts should be included in land uses
3- Locating shops and schools within the walking distance of homes helps reducing the
need of travel. (55)
c) Access Control
1- For a new arterial, a direct access should be permitted only in limited locations.
2- Potentially dangerous locations such as intersection and poor visibility are not
allowed to have any access. (15)
2.6 Road Safety Audit History
Road safety audit procedures were developed in 1989 by British traffic engineers and
evolved from a tool used by railway engineers to examine safety issues on railways.
RSA were soon adopted by Australia, New Zealand, Denmark, and many other
developed countries in the early 1990s. The development of the road safety audit
procedures was refined before adoption by the American transportation community. (16)
In 1996, the FHWA sponsored a tour of Australia and New Zealand to study their road
safety audit programs to learn strategies on how to implement road safety audits in the
United States. From the lessons learned, FHWA sponsored a road safety audit workshop
in St. Louis to develop procedures to be used in the road safety audit pilot program. The
first pilot program included thirteen states and provided a basis for use of road safety
audits in the United States. (16)
As road safety audits have gained popularity in the United States they have also gained
recognition and acceptance in other parts of the world. The Asian Development Bank, in
collaboration with United Nations Economic Commission for Europe and the World
Bank, has recently sponsored the use of road safety audits and has published their own
toolkit to be used in conducting a road safety audit. Countries around world are starting
to realize the low cost tool of saving lives. (16)
There are two different safety auditing processes that can be used. The first one is the
Road Safety Audit (RSA) that looks at projects both at design stage and during
operational stage. The second safety audit process used is Road Safety Inspection (RSI)
that looks at projects only during operation and focusing solely upon safety issues. RSI
also focuses more on safety issues associated with the roadway, all road users, operating
under all environmental conditions, and to identify the safety issues associated with the
existing facility.(16)
17
Road safety audit on existing road is similar to road safety inspection, for this reason
road safety audit and road safety inspection will be used interchangeably for the rest of
chapters in this thesis.
2.7 Definition and Principles of RSA and RSI
The national association of road transport and traffic authorities in Australia that is
called as Austroads defines a road safety audit as “....a formal examination of an
existing or future road or traffic project, or any project which interacts with road users,
in which an independent, qualified examiner looks at the project’s accident potential and
safety performance”. (17)
PIARC (Permanent International Association of Road Congresses) also defines a Road
Safety Audit as a “formal systematic road safety assessment of the road or road scheme
carried out by an independent, qualified auditor or team of auditors who reports on the
project’s accident potential for all kinds of road users”. (18)
Although the given definitions above includes reviews of existing roads, the current
international understanding of road safety audits refers to examinations conducted in the
planning and the design stages of road projects (which include new projects but also redesign projects) before or shortly after a road is opened to traffic or the measure is
completed.
From the definitions above, the purpose of road safety audit is to identify potential safety
problems for all road users in all road projects and eliminate those safety problems and
also to ensure that countermeasures to eliminate and reduce the problems are fully
considered. The scope of safety audit is to minimize number of accidents and severity
and to ensure that all new highway schemes operate as safely as applicable. It is clear
that consideration is given to enhance the safety of all road users rather than vehicles
only.
Road safety audit implies an independent detailed systematic and technical safety check
relating to the design characteristics of a road infrastructure project and covering all
stages of road safety audit from planning to early operation.
A Road Safety Inspection (RSI) is a systematic field study, conducted by road safety
expert(s), of an existing road or section of road to identify any hazards, faults and
deficiencies that may lead to serious accidents. (19)
Road safety inspection involves systematic assessment of the safety standard of an
existing road, in particular with respect to hazards related to traffic signs, roadside
18
features, environmental risk factors and road surface condition. The main purpose of a
road safety inspection is to identify traffic hazards and suggest measures to correct these
hazards. (19)
Road safety inspections are, to a large extent, based on similar checklists and procedures
as those applied in road safety audits. The only difference among the two is that road
safety audits can be applied during the planning of new roads, whereas road safety
inspections is only carried out on existing roads.
2.8 Steps of Road Safety Audit
Basically there are eight steps for conducting road safety audit as shown in the figure 3.0
below and there explanations as follows.
Step 1: Identify Project or Existing Road to Be Audited
This is the first step of road safety audit in which the main objective is to identify the
existing road to be audited and to set parameters for the RSA as seen from figure 3
below. Some of the reasons that make a road or intersection to be audited are:
1-Roadway sections where there are general safety concerns
2-Roadway sections with high crash levels, high traffic volume, geometric roadway and
associated design issues
3-Sections scheduled for overlay projects or school zones that have dangerous aspects
associated with them. (20)
Once a roadway or intersection is selected, parameters need to be set that will define for
client what work will be accomplished and the parameters should define the scope,
scheduled for completion, team requirements, audit tasks, formal audit report contents
and formats and the response report expectations.
Step 2: Select RSA Team
At this stage of RSA, the client or project owners should select the RSA team leader and
together they should select the remaining individuals that will be on the RSA team. The
team should include individuals with expertise in the following fields:
1- Traffic engineering
2- Design
3- Maintenance and safety engineering
4- Expertise in pedestrians and bicyclist, young and older pedestrians, older drivers,
local knowledge, human factors, law enforcement and project scoping. (20)
19
Figure 2.3 Road safety audit process. (21)
This group of experts provides all the necessary knowledge and experience to the
process and also the freedom and ability of auditors to comment frankly on potentially
controversial safety issue is crucial to the success of RSA.
Step 3: Conduct a Pre-Audit Meeting to Review Project Information and Drawings
At this step of RSA, the pre audit meeting should provide all team members with an
overview of the process that the team is undertaking. The client or project owner will
then need to provide all relevant information’s about the project to be audited, this
information’s includes road function, classification, environment, traffic and
environment characteristics of the road and adjacent road network, crash data detailing
the location, and aerial photographs. (20)
Other usual information’s if available includes resident complaints, police observations,
bicycle and pedestrians use and any school zones on the project.
20
Step 4: Review of Project Data and Conduct a Field Review
This is the most important step in the RSA process; the field reviews should see the
project at least two different times of day. Usually the team will walk through the
segment together and note anything that will affect the safety of the road. Standards and
policies can be a starting point. Photos and video should be taken of all issues to help in
writing the final RSA report. The RSA team should look at physical evidence of past
crashes and off road excursions which could include:
1- Damage to curbs, roadside barriers, trees, utility poles, delineator posts, and signs
2- Scuff marks on curbs and concrete barriers
3- Skid marks, broken glass, oil patches on the road
4- Vehicle tracks or rutting in the ground adjacent to a roadway. (20)
Step 5: Conduct Audit Analysis and Prepare Report of Findings
At this step, the RSA team will finalize the RSA findings and develop suggestion in
mitigating them. Additionally the audit team should establish how they wish to evaluate
risk from certain features and how to prioritize the suggestions given.
Step 6: Present Audit Findings to Project Owner/Design Team
One important aspect of this step is to share with the project owner the key findings and
suggestions identified in the RSA report and see if they fit in with the project goals.
At this step the team leader also needs to remind the owner that the intent of the RSA
was to identify opportunities to improve safety and it is not a critique of the road. It is
also important to gather additional information from the owner about safety
recommendations at specific areas. This will allow the RSA team to look back at the
project and to modify any recommendations. (20)
Step 7: Prepare Formal Response
This is the stage of RSA that requires the project owner to explain what RSA
recommendations are going to be implemented and what are not going to be. Below are
some points to be considered at this step:
1- Is the RSA report finding within the scope of the project?
2- Would the suggestion made in the RSA report address the safety issue?
3- Will the suggestion made in the RSA report lead to mobility, environmental, or other
non safety related problems?
4- What would be the cost associated with implementing the suggestions?
5- Are there more cost-effective alternatives that would be equally effective? (20)
Step 8: Incorporate Findings in to the Project When Appropriate
This step is to implement the safety recommendations found in the RSA report and to
ensure the RSA process was a learning experience. The project owner will need to
21
ensure that the agreements described in the response report are completed as described
and in the time frame documented.
2.9 Stages for Conducting a Road Safety Audit
Basically there are six stages at which road safety audit can be conducted, the stages are
described below as follows:
1. Feasibility Study (Concept Design);
2. Preliminary Design;
3. Detailed Design
4. Construction
5. Pre-Opening to Traffic; and
6. Existing Road Audit.
Stage 1 - Feasibility Study / Concept Design
At this stage of RSA, some aspects like route options, layout options or treatment
options can be examined during feasibility stage audits. They allow an assessment of the
relative safety performance of scheme options and identifying specific needs of various
road users. By providing a specific safety input at this stage of a scheme, road safety
audit can influence fundamental issues such as route choice, standards, impact on and
continuity with the existing adjacent network, and intersection or interchange provision.
(22)
Stage 2 - Preliminary Design
At this stage of audit, issues to be considered typically include horizontal and vertical
alignments, and intersection layouts. Where land acquisition is required, the draft design
stage audit should be undertaken before the title boundaries are finalized. It should be
noted that once this stage of design is completed, and land acquisition and other
associated matters are finalized, subsequent changes in road alignment become much
more difficult and costly.
Stage 3 - Detailed Design
This audit stage takes place on the completion of the detailed design but before the
preparation of contract documents. Some typical considerations at this stage include
geometric layout, line markings, signing, delineation, traffic signals, lighting,
intersection details, clearances to roadside objects, landscaping and provision for
vulnerable road users.
22
Stage 4 - Construction
All construction sites are often places of confusion where the traffic route and traffic
control devices are changed from their usual state. It is important that good traffic
control and guidance be given to motorists to safely guide them through the construction
zone and to protect the road workers. Some of the concerns at road works include
signing, delineation and roadside objects. Construction projects of substantial size
should be safety audited by day and by night. (22)
Stage 5 - Pre-Opening to Traffic
This stage of audit involves a detailed inspection of a newly completed work (new or
modified scheme) prior to its opening to traffic. This usually involves inspection by the
audit team as motorists and as pedestrians where appropriate.
If cyclists are to use the road, their needs and safety should also be considered.
Inspections should be carried out by day and by night as some night time associated
problems may not be obvious during the day. (22)
Stage 6 - Existing Road Audit
Road safety audit of an existing road is aim to ensure that the safety features of the road
are compatible with the intended purpose of the road and to ensure that these are at an
appropriate level of safety.
As the use of a road changes over time, this audit therefore also use to identify any
feature which may develop into a safety concern, this stage of audit is independent of the
first five as it can be carried out at any time on an existing road. (22)
At any or all stages of the projects RSA can be conducted. In general audits carried out
in earlier stages get more potential benefits. That is why it is easier to change a line on a
plan than to remove the problem by reconstruction once the road is opened.
2.10 Review of Existing Practices Regarding Road Safety Inspection in Different
Countries Including Africa
Countries worldwide using the techniques of road safety audits and road safety
inspection increases rapidly especially in most advanced countries since the middle of
1980s.
The degree of implementation of RSI varies across countries. Some countries have
already published handbooks and guidelines for RSI, and some other countries have not
even started the process of implementation. In this section, the implementation status of
each country will be described as well as the different approaches in the countries.
This section presents the existing road safety inspection practices in some countries
around the world. The countries are United Kingdom, New Zealand and Australia, Italy,
France, Austria, Norway, Kenya, Benin Republic and Tanzania. Worldwide, the RSI
23
concept has proven to be highly effective in identifying and reducing the crash potential
of roadway projects.
Moreover in many countries all over the world RSA/RSI application is growing rapidly,
since it is considered an important element of a road safety program. In majority of these
countries, manuals have been developed and RSA/RSI is being carried out for years. The
application concept is not exactly the same for applying countries but the general idea
behind is the same.
Figure 2.4 Current use of road safety audits in Europe (18)
Figure 2.5 Current use of road safety inspection in Europe (18)
24
From the figure 2.4 and figure 2.5 above it can be seen that both road safety audit and
road safety inspection are being carried out in many European countries as a tool for
safety.
Also the figure below shows the application of road safety audit in United State which
shows majority of the countries have either adopted road safety audit completely or they
are in piloting stage
Figure 2.6 Current use of road safety audit in United States. (23)
2.10.1 United Kingdom
RSI in United Kingdom is based on the Road Inspection Manual, issued in 2004. The
objectives of the manual were to define hierarchies of carriageways, footways and cycle
tracks for inspections, to recommend the procedures and the minimum frequencies for
the inspections used to determine routine maintenance tasks, and to encourage
consistency in the standards for the inspections. (24)
RSI in UK fall within the remit of Highways Authorities maintenance offices and is
therefore part of the routine maintenance, and from that ensures the concentration on
short term measures and improvements.
In the UK the inspections are divided into two types as follows:
(1) Safety Inspections (SI): During the Safety Inspections SI all defects likely to create
danger or serious inconvenience to users of the network have to be identified. Remedial
measures to correct such defects should take place within 24 hours.
25
SI may be carried out from a slow moving vehicle, or on foot. In order to ensure the safety of the
inspection team, the on-foot inspection should be done along the footway, and not along the
carriageway. (13)
(2) Detailed Inspections (DI): The Detailed Inspections (DI) is designed according to the
Road Inspection Manual (RIM) to record only those types of defects likely to require routine
maintenance. These defects do not require urgent repair. Nevertheless, in case of identifying
immediate or imminent hazards during the DI, these should also be noted. (24)
2.10.2 Austria
The legal basis for RSI in Austria is the RVS guideline, which was published in 2007.
After that a handbook “Handbook for Carrying out Road Safety Inspection” was
developed to supplement the guideline and support the systematization and ensure a
standardized and structured approach for this instrument in Austria.
In Austria, Road Safety Inspections of motorways and expressways started in July 2003.
Between 2003 and 2007 several sections have been inspected by Austrian Road Safety
Board. In the following years pilot-inspections on the secondary road network were
carried out. In the course of production of the RSI handbook pilot inspections in urban
areas and municipalities were conducted. (24)
2.10.3 Italy
In Italy there is a manual called Operative procedures for Safety Inspections on TwoLane Rural Roads. This manual was developed by the University of Catania, and its use
has spread out to all Italian provinces and the Local Agencies in Sicily, Calabria and
Campania on a volunteer basis. The manual was published in 2005 and revised in 2008.
The manual describes the road safety operative procedures adopted by the IASP research
program. (24)
The manual Operative Procedures for Safety Inspections on Two Lane Rural Roads
requires several site inspections as follows:
(1) Preliminary inspection
(2) General inspection
(3) Detailed Inspection and
(4) Night time inspection. (24)
The main objectives of the above are as follows: preliminary inspection is trying to
understand the general road safety conditions, general inspections is to obtain
information about the safety issues and their location, detailed inspection In order to
carry out a detailed inspection of the sites which present specific safety issues, and night
time inspections is to understand how the road is perceived during the night in which the
main focus is on road signs, delineation and visibility.
26
2.10.4 France
In France Road Safety Inspections are carried out periodically on the entire national road
network at a three year interval. These periodical inspections have just started in 2009,
after the decision of the Inter-ministerial Committee for Road Safety in February 2008.
An extensive “Methodological Guide for Road Safety Inspections” has been published
in 2008, which is the basis for this report. (24)
2.10.5 Australia and New Zealand
In Australia and New Zealand the inspection of existing roads is part of the Road Safety
Audit (RSA). The guidelines for this instrument were first published in 1993 in New
Zealand and in 1994 in Australia. The responsible institution for RSA in these two
countries is AUSTROADS, the association of Australian and New Zealand road
transport and traffic authorities.
In New Zealand it is required to carry out RSA on the whole road network (both national
and local government); in Australia only state road projects must be audited. In Australia
local government projects must be audited only if these projects are fully or partly
funded by the state. In both countries, Australia and New Zealand, inspectors must be
trained and experienced. (24)
2.10.6 Norway
The Norwegian Public Roads Administration published the Handbook Road Safety
Audits and Inspections in 2006. According to this handbook RSI in Norway consists of
three steps: Preparation, Inspection and Reporting. The handbook suggests the use of the
new method for Road Safety Inspection. In this new method more time is dedicated to
preparation, while by the traditional method reporting was the most time-consuming
step. (24)
These changes were the result of the following developments: In the preparation step the
road section is driven through several times, pictures are taken every 20 meters or a
video recording is performed, which will be reviewed afterwards in the office. If this
documentation is carried out beforehand, the field inspection will then be less timeconsuming, when completed forms with pictures and comments are being used.
The inspection team should have an inspection leader, members with road safety
knowledge, members with local knowledge of the road network (this is different from
other countries where a fresh looks are used) and members with contracting competence.
27
It can also be appropriate to involve the police, the municipality and specialist with
knowledge of tunnels, bridges, signs and markings, operation and maintenance, as well
as road users. The number of members can vary depending on complexity, area, type
and length of the section. The inspection always starts with an initial meeting, with
attendance by all parties.
2.10.7 Kenya
The Kenya road safety program started in 1980 by Ministry of Transport and
Communications
Kenya, the program were supported by Finland, proposed
organizational measures, enforcement, an accident investigation committee, driver
training, vehicle inspection, road planning and maintenance, first aid training,
information and education, and road safety research. The objective of the project was to
improve road safety in Kenya. (25)
The Kenya road safety program came to an end in 1991. As part of the conclusion of this
program the National Road safety Council prepared a Cabinet memorandum on
measures to enhance safety on Kenyan roads which recommends several
countermeasures to be employed.
2.10.8 Benin Republic
A road safety program in Benin begins during the year 1995, a program consisting of
three projects were conceived in 1995. These projects make up the road safety part of
the Transport Sector Program, which has been initiated with assistance from the World
Bank. The projects entail
(a) Creation of a data bank for road accident statistics;
(b) Implementation of an awareness and education program;
(c) Strengthening of the centers for technical control of vehicles.
The main obstacle to realizing the road safety program has been a lack of funds to
implement the programmed successfully. (25)
2.10.9 Tanzania
An extensive road safety program started in July 1996 (United Republic of Tanzania,
1996). The program comprises all areas of road safety and, if implemented, should have
a great potential for reducing the road accident problem of Tanzania. However, as of
February 1997, the government had not yet approved the program. (25)
The main objectives and activities of the program are:
28
(1) Establish a road safety organization capable of managing a multi-sector integrated
approach to the road safety problem with long- and short-term plans.
(2) Increase the quality of life in Tanzania by preventing accident occurrence and by
minimizing the consequences of road accidents.
(3) Prolong the life of the road network through effective vehicle and axle load control.
(25)
29
CHAPTER 3
3 METHODOLOGY AND EXPLANATIONS OF ROAD SAFETY AUDIT
3.1 Introduction
The Road Safety Audit can be applied to specific operating and maintenance activities
on existing roads as well as for systematic assessment of road safety aspects on existing
roads and road networks.
Some of the inputs or information’s that are necessary needed for road safety audits on
existing road are road function, traffic data, speed data and accident data. These data
support auditors for better performing the audit of the road. By the help of these data
auditors can clarify the road function, have idea about the typical accident types, volume
of traffic, speed levels of different vehicles etc. After getting these data they can
immediately determine the potential hazards and focus on them.
3.2 Methodology for Safety Auditing on Existing Roads
Audit on existing roads started after certain information about the road section are
obtained. Highway section should be audited for both traffic directions. Nevertheless
one site study is never enough to collect auditing information and its evaluation. In many
cases two or more auditing studies have to be implemented and at least one survey must
be conducted at night.
One of the benefits of the RSA process is the cooperative interaction created by the
members of the audit team. The knowledge and experience of the team as a whole are
greater than the sum of these attributes as vested in the individual members, so the
process benefits from being conducted by a team. While three members in a team may
be adequate for some project types, the number may not be sufficient for larger, more
complex projects or those requiring specific expertise. (26)
30
The best practice is to have the smallest team that brings all of the necessary knowledge
and experience to the process.
All of the observations achieved during the audit are recorded on the safety audit
checklists and forms prepared in a special format as illustrated on the subsequent
paragraphs. Below are examples of some features to be observed during the field survey;
a- Locations in which shoulder widths are inadequate
b- Markings that are not in existence or in a complex condition ( old and new
markings mix each other)
c- Problematic road side zones that include dangerous features which can create
specific danger within the clear zone width (Tress, Utility Poles).
d- The existence of various kinds of trees and other vegetation which obstruct the
sight distance of the drivers
e- Improper location of the bus stops
f- Non guard-rail sections
g- Concrete structures and dangerous wall endings
h- Improper information signs
i- Improper junction design
j- Improper drainage structures. (26)
All these features above and many others are recorded on the safety audit checklist on
existing road during the field survey, also photographs and video records were also
made during the site visits which are used to make final discussions and evaluations.
3.3 General Project Data Required for Road Safety Audit on Existing Road
In order to carry out a road safety audit on existing road, there are many important data
or information’s required about the particular road section selected for
auditing/inspection, the basic inputs or data’s are described below.
3.3.1 Functional Classification of the Road
Functional classification is a way by which streets and highways are grouped into
classes, or systems according to the character of traffic service that they are intended to
provide. This classification recognizes that individual highways do not serve travel
independently. Rather, most travel involves movement through networks of highways
and can be categorized relative to such networks in a logical and efficient manner. Thus,
functional classification of highways is consistent with the categorization of travel. (43)
The roads making up the functional systems differ for urban and rural areas. The
hierarchy of the functional systems consists of principal arterials (for main movement),
minor arterials (distributors), collectors, and local roads and streets. But however, in
31
urban areas there are relatively more arterials with further functional subdivisions of the
arterial category whereas in rural areas there are relatively more collectors with further
functional subdivisions of the collector category. (27)
Rural roads consist of facilities outside of urban areas. The names provided for the
recognizable systems are principal arterials (roads), minor arterials (roads), major and
minor collectors (roads), and local roads. (27)
The rural principal arterial highway consists of the following service characteristics:
a. Corridor movement with trip length and density suitable for substantial
statewide or interstate travel.
b. Movements between all, or virtually all, urban areas with populations over
50,000 and a large majority of those with populations over 25,000.
c. Integrated movement without stub connections except where unusual geographic
or traffic flow conditions dictate otherwise. (27)
The rural minor arterial road system, in conjunction with the rural principal arterial
system, forms the following service characteristics:
a. Linkage of cities, larger towns, and other traffic generators those are capable of
attracting travel over similarly long distances.
b. Integrated interstate and inter county service.
c. Internal spacing consistent with population density, so that all developed areas of
the state are within reasonable distances of arterial highways.
d. Corridor movements consistent with items through with trip lengths and travel
densities greater than those predominantly served by rural collector or local
systems. (27)
The rural collector routes generally serve travel of primarily between counties and
constitute those routes on which predominant travel distances are shorter than on arterial
routes. Consequently, more moderate speeds may be typical. (27)
The local road system, in comparison to collectors and arterial systems, primarily
provides access to land adjacent to the collector network and serves travel over relatively
short distances. The local road system constitutes all rural roads not classified as
principal arterials, minor arterials, or collector roads.
Road function is important input for road safety audit. When starting an audit the
auditors should have information about the character of the traffic that is based on the
road function. All roads should be evaluated in their own function because different
types of roads have different types of safety situations.
For example the prevailing risk of having fatal accidents is bigger in rural areas
compared to urban areas thus the safety solutions of these areas are also different. The
32
function of a road should be clear to all road users, and a well planned and defined road
hierarchy can assist road users in providing a safe road network.
Figure 3.1 Illustration of Access-Mobility Relationship. (28)
Figure 3.0 above shows the relationship between mobility and land access, as well as
how Principal Arterials, Collectors and Local Roads proportionally serve their functions.
Arterials provide mostly mobility, Locals provide mostly land access, and Collectors
strike a balance between the two.
Also from the figure 3.0 above, it can be observed that those roadways that provide a
high level of mobility are Arterials, those that provide a high level of accessibility are
Locals roads and those that provide a more balanced blend of mobility and access are
called Collectors. (28)
3.3.2 Traffic Data
Highway Transportation Surveys are performed to establish a basis for transportation
planning process and they contribute to the highway design, construction, maintenance
and management facilities. Transportation surveys are accomplished according to the
Annual Transportation Survey Program carried out by the Planning Departments of
Road Authorities. They are achieved in order to determine traffic characteristics of
highways by using modern counting devices and techniques.
33
All pertinent information such as volume, speed and accident data is formed by these
surveys. The subsequent paragraphs represent the definitions of these data and explain
relationship of the data and the road safety audits on existing road.
3.3.3 Volume Data
In order to carry out safety audit on existing road, traffic volume data is one of the
necessary inputs required. Traffic volume studies are conducted to determine the
number, movements, and classifications of roadway vehicles at a given location. These
data can help to identify critical flow time periods, to determine the influence of large
vehicles or pedestrians on vehicular traffic flow and to document traffic volume trends.
The length of the sampling period depends on the type of count being taken and the
intended use of the data recorded. For example, an intersection count may be conducted
during the peak flow period. If so, manual count with 15-minute intervals could be used
to obtain the traffic volume data. (5)
Generally there are two methods available for conducting traffic volume counts 0n
existing roadway.
a) Manual Traffic Volume Count
Manual traffic count is conducted without the help of any equipment. Most applications
of manual counts require small samples of data at any given location. Manual counts are
sometimes used when the effort and expense of automated equipment are not justified.
Manual counts are necessary when automatic equipment is not available or the data
required is small. (29)
b) Automatic Traffic Volume Count
The automatic count method provides a means for gathering large amounts of traffic
data. Automatic counts are usually taken in 1-hour intervals for each 24-hour period.
The counts may extend for a week, month, or year. When the counts are recorded for
each 24-hour time period, the peak flow period can be identified. (29)
Generally Volume data is an important input for road safety audit on existing road or
any other stage of the audit, and the data should always be accurate and reliable. Only
reliable and accurate data is needed to correctly identify problems, risk factors and
priority areas, and to formulate strategy, set targets and monitor performance. Without
this, there will be no significant, sustainable reductions in exposure to crash risk or in the
severity of crashes.
3.3.4 Speed Data
Speed data is also an essential data needed for road safety audit on existing road. Design
speed is a selected speed used to determine the various design features of the roadway.
34
Geometric design features should be consistent with a specific design speed selected as
appropriate for environmental and terrain conditions. (27)
Low design speeds are generally applicable to roads with winding alignment in rolling
or mountainous terrain or where environmental conditions unfavorable and high design
speeds are generally applicable to roads in level terrain or where other environmental
conditions are favorable. Intermediate design speeds would be appropriate where terrain
and other environmental conditions are a combination of those described for low and
high speed. (27)
All geometric design elements of the highway are affected in some way by the selected
design speed. Some roadway design elements are related directly to and vary
appreciably with design speed, such elements include horizontal curvature, super
elevations, sight distance, and gradient.
Other elements are less related to design speed, such as pavement and shoulder width
and clearances to walls and traffic barriers, the design of these features can however,
affect vehicle operating speeds significantly.
The selection of a particular design speed for a particular road is influenced by the
following:
a. The functional classification of the highway
b. The character of the terrain
c. The density and character of adjacent land uses
d. The traffic volumes expected to use the highway
e. The economic and environmental considerations. (27)
Typically, the order of speed selection is as follows, an arterial highway warrants a
higher design speed than a local road; a highway located in level terrain warrants a
higher design speed than one in mountainous terrain; a highway in a rural area warrants
a higher design speed than one in an urban area. (27)
When conducting audit on acceleration, deceleration lanes, barrier design, exit and
entrance parts of the roadside facilities, desired clear zone width, stopping and passing
side distance, all these features are design based on the speed data. On the other hand,
prevailing speed surveys may reveal speeding related casualties.
3.3.5 Accident Data
An accident database is needed for accurate assessment of the road safety situation. In
order to be useful, the record needs to cover data on deaths and casualties and the
35
circumstances of the accidents. This will help for safety improvements and implement
appropriate measures designed to solve specific problems.
The main processes of producing an accident database include an accident reporting and
recording system, storage and retrieval system, an analysis system, and an effective
dissemination system. (30)
The data collected for all recorded accidents needs to cover the following questions:
a. Where accidents occur;
b. When accidents occur;
c. What type of car involved;
d. What was the result of the collision?
e. What were the environmental conditions?
f. How did the collision occur? (30)
Accident data is very useful for designing appropriate countermeasures, producing
plans, monitoring effectiveness, and carrying out research.
3.3.6 Safety Audit Checklist on Existing Road
The recommended structure of safety audit checklist on existing road is illustrated
below.
SAFETY AUDIT CHECKLIST ON EXISTING ROAD
Date:
Weather:
CONTROL
STATION
NUMBER(CSN)
KM
DISTANCE
M
Table 3.1 Road Safety Audit Checklist
36
TYPE OF
HAZARD
Conducted By:
COMMENT
3.3.7 List of Hazards
All the hazards on existing roadway were categorized and classified in to two different
groups as road side and road design hazards as shown in the table below:
Table 3.2 Hazard List
A-Road Design Hazards
Hazard Number
Hazard Name
1
Shoulder missing
2
Shoulders too narrow
3
Shoulder unpaved
4
Improper junction design
5
Improper connection to shop, petrol station, commercial activities
6
Improper connection to small access road
7
Improper connection to roadway
8
Improper median opening
9
Limited sight distance
10
Improper or dangerous pedestrian crossing
11
Too small radius of horizontal curve
12
Too small radius length of vertical curve
13
Speed limit too high
14
Speed limit too low
15
Improper vertical sign
16
Improper horizontal sign
17
Potholes
B-Road Side Area Hazards
18
Dangerous fixed object on the roadway
19
Dangerous fixed object on road side or median
20
Dangerous fixed object on road island
21
Temporary road narrowing (e.g. bridge)
22
Fixed massive poles near road or in the median
23
Road edge deterioration
24
Big trees or trees close to the road
25
Dangerous bridge piers
26
Dangerous hedge
27
Dangerous cut form
28
Dangerous free stones or rocks
29
Dangerous support for signs(advertisement or road information sign)
30
House or other building so close to road
37
Table 3.2 Hazard List (continuation)
31
Steep edge slope without guardrail
32
Dangerous guardrail start and end
33
Improper culvert design on the road side
34
Improper commercial activities on the roadside
35
Improper bus stop design
36
Missing sign
37
Use of non standard sign
3.4 Roadside Safety
The roadside safety is the prior concept of the road safety audit (RSA) on existing roads.
Roadside safety concept includes information about the clear zone area and hazardous
obstacles locations for both at project level and for analysis of existing road sections.
Run off road (leaving carriageway / loss of control) results into fatal accident if crash
involves dangerous objects on the roadside. The severity of this type of accident may
also be influenced by the physical characteristics of the roadside environment (side
slopes, etc.). The Highway Project Engineers have to give attention to minimize the
number and severity of accidents by designing roads with more gentle side slopes and by
arranging safe zones along the road sides. (31)
Flat and traversable, stable slopes can minimize further overturning if vehicle leaves the
carriageway. Roadsides, in which obstacles cannot be removed with a reasonable cost,
should be controlled by installing guardrails. The guardrail should be given illuminating
features so as to be readily visible to motorists. (31)
3.4.1 Safety Zone
Safety zone addresses the area outside the roadway and is an important component of
total highway design. There are numerous reasons why a vehicle leaves the roadway,
including driver error and behaviors. Regardless of the reason, a roadside design can
reduce the seriousness of the error and the subsequent consequences of a roadside
encroachment.
From a crash reduction and severity perspective, the ideal highway has roadsides and
median areas that are flat and unobstructed by objects. It is also recognized that different
facilities have different needs and considerations, and these issues are considered in any
final design.
Along both sides of a road, there should be a recovery area (a clear zone) permitting the
driver to regain control of a vehicle which for some reason has left the roadway. The
38
recovery area should have a gentle design with flat slopes to prevent the vehicle from
rolling over. It should also be clear from hazardous objects which can cause injuries to
the driver or passengers. (32)
The typical design of the clear zone is shown in figure below.
Figure 3.2 Roadside Safety Zone Designs (33)
Some of the hazardous objects associated with roadside are described below;
a. Bridge piers, abutments, railing ends
b. Rocks with diameters > 0.2 m
c. Trees with diameters > 0.1 m
d. Cross (transverse) pipe opening widths larger than (750 mm)
e. Box culverts and cattle passes
f. Approach (parallel) pipe height larger than (600 mm)
g. Cut slopes (rough)
h. Steep in slopes
i. Approach slopes steeper than 6:1
j. Signs/luminaries/traffic signals with non-breakaway supports
k. Utility poles (lighting)
l. Walls (unless crashworthy). (32)
Adequate clear zone distance between the edges of traffic lanes and roadside
obstructions has been shown to be a very important safety factor. Out of control vehicles
leaving the roadway should have a reasonable opportunity to recover control and return
to the roadway without overturning or colliding with roadside obstacles.
39
To prevent fatal accidents within the clear zone, the hazards that are located in the safety
zone should be;
(1) Taken away or removed
(2) Replace it with a non-hazardous equipment
(3) Redesigned or shielded by traffic barriers or crash cushion. (32)
According to AASHTO, the width of clear zone is found out by evaluating the annual
average daily traffic (AADT), the design speed and cut or fill slope section of roadside
slope. Based on this data, the required widths of safety zone are given table 3.1 below.
Table 3.3 Recommended Clear Zone Width. (33)
3.5 Basic Explanations of Typical Hazards
Some of the typical hazards associated with either roadside or road design are described
and explained below.
a) Utility Poles
Utility pole crashes are fixed-object crashes that involve vehicles leaving the travel lane
and striking a utility pole.
40
Utility poles can also contribute to the severity of other crash types. Many crashes are
not classified as run of roadway or fixed-object crashes where one or more vehicles
strike a utility pole. Crashes are often classified by “first harmful event.” In some cases,
striking the utility pole is a secondary event that may be as severe as, or more severe
than, the first harmful event. Crashes involving utility poles as secondary events easily
go unnoticed when examining the total magnitude of the utility pole crash problem. (34)
Utility poles are one of the most substantial objects that are placed on roadsides
worldwide. They are substantial both in number and in structural strength. Because of
the structural strength of utility poles, these crashes tend to be severe.
b) Trees
Beside the utility pole crashes, another higher crash rates and fatalities are also
associated with roadside trees. One of the most common causes of fatal and severe
injury accidents on rural roads in particular are fixed objects. Trees are the objects most
commonly struck in run off road collisions, and tree impacts are generally quite severe.
A collision between vehicles and trees is one of the major types of traffic fatality. Fatal
tree crashes were most prevalent on local rural roads, followed by major rural collectors.
The crash effects of nearby trees along high-speed, rural roadways are indisputable.
County and township roads that generally have restrictive geometric designs and narrow,
off-road recovery areas account for a large percentage of the annual tree-related fatal
crashes. Existing trees often pose greater risk than trees that have been placed along new
or reconstructed roads. (35)
c) Walls and Concrete Structures
Walls and concrete structures located in critical positions are not consistent with a
forgiving roadside. Walls and concrete structures are made by high structural strength of
materials. These types of roadside structures cause more serious injury and damage
accidents.
d) Improper Signing and Marking
Driving is mainly based on visual information input. There are many types of visual
information, but road signs and road markings are important because they can provide
relevant information for the driver to execute his or her task safely. Therefore, road
signing may constitute an important road safety factor. The characteristics of road
signing may have negative effects on traffic safety in the following cases:
a. The driver does not detect the sign/marking;
b. The driver is not able to identify the sign/marking properly;
c. The driver does not understand the sign/marking;
d. The driver does not have enough time to decide and take the action(s) needed;
41
e.
f.
g.
h.
The sign/marking does not meet the driver’s expectations;
The sign’s message is not heeded by the driver;
The information on the sign is wrong / inappropriate;
The driver does not remember the sign for the necessary time. (36)
e) Intersections
Many accidents on rural highways occur at intersections. Intersections are locations
where two or more roads are connected or cross each other. The crossing and turning
maneuvers that occur at intersections create risks for vehicle-vehicle, vehicle-pedestrian,
and vehicle-bicycle conflicts, which may result in crashes. Thus, intersections are likely
points for higher traffic crashes.
f) Improper Access Management
Access regulation along roadway is referred to as access control; it is achieved through
the regulation of public access rights to and from properties abutting the highway
facilities. These regulations generally are categorized as full control of access, partial
control of access, access management, and driveway/entrance regulations. The principal
advantages of controlling access are the preservation or improvement of service and
safety. (27)
Access control, which is the way of regulating public access to and from properties
abutting highway facilities, is one of the most significant factors in the safe, efficient
operation of a highway. Full control of access is the most important single safety factor
that may be designed into new highways. (27)
The principle of full control of access is invaluable as a means for preserving the
capacity of arterial highways and of minimizing accident potential. On the other hand,
improper access control may create great potential for the traffic accidents.
g) Improper Bus Stop Design
Improving facilities for public transportation is one of the main concerns of the urban
network improvements. In this concept there must be safe areas for busses to stop and
take passengers without interrupting the traffic stream. In some cases, bus stop designs
are improper thus creating danger for public transportation users and the other drivers.
At some other cases there are not any safe areas for bus stops.
h) Improper Drainage Structures Design
Drainage is one of the most critical elements in the design of a highway. Highway
drainage facilities carry water across the road and remove storm water from the roadway
itself. Drainage structures include bridges, culverts, channels, curbs, gutters, concrete
42
pipes and various types of drains. These elements should be designed, constructed, and
maintained considering both hydraulic efficiency and roadside safety.
Ends of large drainage structures, causes safety problems for errant vehicles, therefore
culvert openings should be covered with traversable grates, where practical, to prevent
trapping a vehicle.
It was stated by National Cooperative Highway Research Program (NHCRP) that:
a. The improper design of roadside (and of wide medians, which is equivalent to
roadside) drainage elements can increase accident severity.
b. The improper placement of drainage inlets / outlets may cause improper
drainage resulting in a reduced friction hazard and thus contributing to the
occurrence of an accident. (37)
i) Improper Medians and Median Openings
A median is the portion of a highway separating opposing directions of the traveled way.
Medians are highly desirable on arterials carrying four or more lanes. Median width is
expressed as the dimension between the edges of traveled way and includes the left
shoulders, if any.
The principal functions of a median regarding safety are to separate opposing traffic,
provide a recovery area for out of- control vehicles, provide a stopping area in case of
emergencies, allow space for speed changes and storage of left-turning and U-turning
vehicles, minimize headlight glare, and provide width for future lanes. (27)
In urban areas there are some additional benefits of median such as it may offer an open
green space, also provide a safe area for pedestrians crossing the street, and may control
the location of intersection traffic conflicts. For maximum efficiency, a median should
be highly visible both night and day and should contrast with the traveled way. Medians
may be depressed, raised, or flush with the traveled way surface. (27)
Properly designed median barriers minimize vehicle damage and lessen the accident
likelihood of traffic moving in the same direction. A narrow median also does not allow
for emergency departure from the lane.
43
Figure 3.3 Typical Median with Concrete Barrier (21)
j) Improper Selection of Lane and Shoulder Widths
Total roadway width is among the most important cross-section considerations in the
safety performance of a highway. Wider lanes and shoulders normally result in fewer
crashes.
It can be explained that, although the highway design elements such as lane width,
shoulder width, and sight distance restriction are related to accidents, they do not
ordinarily serve as good predictors of accidents. Generally speaking, wider lanes, wider
shoulders, and unimpaired sight distance result in a safer highway. (27)
The capacity of a highway is affected by the lane width. Narrow lanes force drivers to
operate their vehicles closer to each other laterally than they would normally desire.
Restricted clearances have much the same effect. In a capacity sense the effective width
of traveled way is reduced when adjacent obstructions such as retaining walls, bridge
trusses or headwalls, and parked cars restrict the lateral clearance. In addition to the
capacity effect, the resultant erratic operation has an undesirable effect on driver comfort
and crash rates. (27)
A shoulder is the portion of the roadway platform that accommodates stopped vehicles,
emergency use, and lateral support of sub-base, base, and surface courses. In some
cases, the shoulder can accommodate bicyclists. Regardless of the width, a shoulder
should be continuous. With a continuous shoulder, almost all drivers making emergency
stops will leave the traveled way, but with inadequate shoulder, drivers will find it
necessary to stop on the traveled way, creating danger to other road users.
k) Improper Selection of Speed Limit
A speed is often a contributing factor in accidents, but it must be related to conditions. It
is improper to conclude that any given speed is safer than another for all combinations of
different kinds of drivers, vehicles, highways, and local conditions.
44
For a highway with particularly adverse roadway conditions, a relatively low speed may
result in fewer crashes than a high speed, but this does not necessarily means that all
potential crashes can be eliminated by low speeds. Likewise, vehicles traveling on good
roads at relatively high speed may have lower crash involvement rates than vehicles
traveling at lower speeds, but it does not necessarily follow that yet a higher speed
would be even safer. (27)
Safest speed for any highway depends on design features, road conditions, traffic
volumes, weather conditions, roadside development, spacing of intersecting roads, crosstraffic volumes, and other factors. Crashes are not related as much to speed as to the
range in speeds from the highest to the lowest.
l) Improper Fill and Cut Slopes
Fill slopes can present a risk to an errant vehicle with the degree of severity dependent
upon the slope and height of the fill. Providing fill slopes that are 4H:1V or flatter can
mitigate this condition. According to the critical surface condition the fill slopes can be
reduced 3H:1V or more steep but if the fill slope height is high some of the safety
conditions should be thought by designer for road users safety. Also 3H:1V or more
steep side slopes, the surface stability analysis should be considered. (27)
A cut slope is usually less of a risk than a traffic barrier. The exception is a rock cut with
a rough face that might cause vehicle snagging rather than providing relatively smooth
redirection. Analyze the potential motorist risk and the benefits of treatment of rough
rock cuts located within the Design Clear Zone. Conduct an individual investigation for
each rock cut or group of rock cuts. A cost-effectiveness analysis that considers the
consequences of doing nothing, removal, smoothing of the cut slope, and other viable
options to reduce the severity of the condition can be used to determine the appropriate
treatment. (27)
Cut slopes can be changed by the material type and the topographical conditions of the
road alignment. In high cut slopes; safety for road users and pedestrians along the cut
slope area can be provided by establishing guardrails.
m) Barriers
Roadside barriers are important components in road and bridge project designs when a
hazard is perceived alongside the roadway but also at the same time very dangerous by
increasing accident severity.
Hazards include fixed objects such as non breakaway light and sign posts, telephone
poles, bridge piers and abutments, retaining walls and culverts, trees, rough rock cuts,
boulders, embankments, streams and permanent water bodies.
45
Roadside barriers are also used to separate roadways from pedestrians, bicycle paths and
steep grades, to separate opposing traffic lanes, and to define medians. They are
typically set in the roadway's “clear zone” or “recovery zone”, the area beyond the travel
lane that needs to be kept clear of potential fixed-object hazards. This area’s depth varies
with traffic volume and design speed. (38)
Safety barriers include guard fences (traffic barriers on the edge of a carriageway; if
used in a median they may be referred to as median barriers) and impact attenuators
(devices installed at fixed installations, such as bridge piers; they are also referred to as
crash cushions). (38)
Guardrails not only decrease the accident casualty, but also cause increase severity of
accidents, with wrong design and loss of functionality.
n) Pavement
The selection of pavement type is determined based on the traffic volume and
composition, soil characteristics, weather, performance of pavements in the area,
availability of materials, energy conservation, initial cost, and the overall annual
maintenance and service-life cost. (39)
Important pavement characteristics that are related to geometric design are the effect on
driver behavior and the ability of a surface to retain its shape and dimensions, to drain,
and to retain adequate skid resistance.
Nevertheless, when eliminating crashes is not possible, reducing the severity of a crash
is an important goal. In this sense, more attention is required to other elements of the
roadway system that could be a contributing factor in traffic crashes.
One such contributing factor that has been discussed and evaluated over the years is road
surface characteristics, specifically skid resistance (friction) of roadway pavements
under various weather and aging conditions. (39)
Skid resistance of pavements is the friction force developed at the tire pavement contact
area. In other words, skid resistance is the force that resists sliding on pavement
surfaces. This force is an essential component of traffic safety because it provides the
grip that a tire needs to maintain vehicle control and for stopping in emergency
situations. Skid resistance is critical in preventing excessive skidding and reducing the
stopping distance in emergency braking situations. (39)
46
o) Temporary Work Zones
The driving conditions of work zones differ from normal driving conditions. In addition,
the driving conditions of each type of work zone (short-term, long-term, etc.) may differ
from those of another type of work zone. These factors can result in violations of road
user expectancy, which in turn can lead to congestion, erratic maneuvers, and ultimately
crashes.
The factors found to have contributed to crashes at work zones includes:
a. some aspect of the work zone
b. traffic congestion
c. lane changing
d. vehicles entering and leaving the work zone
e. unexpected presence of flag-person.(39)
3.6 Typical Hazards Countermeasure Selection
Having identified the elements of the road and traffic environment or driver behavior,
which may have contributed to the crashes, it is now important to consider
countermeasures. There are no ‘general’ road safety solutions; for a solution to be
effective, it must be applied to a particular problem, which it is known to affect. It must
be an effective countermeasure. Although a large proportion of crashes are deemed to be
a result of driver error, but however with engineering measures, it is possible to:
a. modify driver behavior
b. modify the road and environment that led to the error
c. make the environment more accepting of human error
The most important aspect of developing solutions is to link the specific
countermeasures to the specific problems identified. The countermeasures could include
engineering, enforcement and education. But enforcement and education
recommendations need to be forwarded to the appropriate agencies for program
development and implementation. (40)
A Crash Reduction Study (CRS) is too focused on low medium cost engineering
solutions that will prove to be very effective with an excellent economic return.
However, in some cases a significant crash reduction may only be achieved through
larger scale, and more substantial improvements. If this is the case, the CRS team would
generally recommend a more detailed study to be carried out to investigate these more
substantive options rather than to delay the overall study pending more detailed analysis.
(40)
The degree to which these more substantive solutions are developed is dependent upon
the CRS brief. The Road Controlling Authority (RCA) may widen the study brief to
include consideration of medium to high cost options. The expertise of the team
47
members may need to be broadened to accommodate this and other aspects such as
traffic flow, environmental impact, mobility, accessibility and sustainability. (40)
There are number of general countermeasures for hazards and problems that can be
applied in order to achieve safe traffic operation for the roads which were proposed
below.
a) Safety Zone
A clear roadside border area is a primary consideration when analyzing potential
roadside and median features. The intent is to provide as much clear, traversable area for
a vehicle to recover as practicable given the function of the roadway and the potential
tradeoffs.
Roadside safety addresses the area outside the roadway and is an important component
of total highway design. There are numerous reasons why a vehicle leaves the roadway,
including driver error and behaviors. Regardless of the reason, a roadside design can
reduce the seriousness of the error and the subsequent consequences of a roadside
encroachment. From a crash reduction and severity perspective, the ideal highway has
roadsides and median areas that are flat and unobstructed by objects. It is also
recognized that different facilities have different needs and considerations, and these
issues are considered in any final design. (40)
It is not possible to provide a clear zone free of objects at all locations and under all
circumstances. The engineer faces many tradeoffs in design decision-making, balancing
needs of the environment, right of way, and different modes of transportation. (40)
Elements such as side slopes, fixed objects, and water are features that a vehicle might
encounter when it leaves the roadway. These features present varying degrees of
deceleration to the vehicle and its occupants. The counter measures to be taken depend
on the probability of a collision occurring, the likely severity, and the available
resources.
According to order of priority, the counter measures according to the Washington State
Department of Transportation are:
a. Removal
b. Relocation
c. Reduction of impact severity (using breakaway features or making it traversable)
and
d. Shielding with a traffic barrier. (40)
48
b) Cut Slope
A cut slope is usually less of a risk than a traffic barrier. The exception is a rock cut with
a rough face that might cause vehicle snagging rather than providing relatively smooth
redirection. Analyze the potential motorist risk and the benefits of treatment of rough
rock cuts located within the Design Clear Zone.
Conduct an individual investigation for each rock cut or group of rock cuts. A costeffectiveness analysis that considers the consequences of doing nothing, removal,
smoothing of the cut slope, and other viable options to reduce the severity of the
condition can be used to determine the appropriate treatment. Some potential options
are:
a. Graded landform along the base of a rock cut.
b. Flexible barrier
c. More rigid barrier
d. Rumble strips. (40)
c) Fill Slope
Fill slopes can present a risk to an errant vehicle with the degree of severity dependent
upon the slope and height of the fill. Providing fill slopes that are 4H:1V or flatter can
mitigate this condition. If flattening the slope is not feasible or cost-effective, the
installation of a barrier might be appropriate.
d) Fixed Objects
Mitigate fixed features that exist within the Design Clear Zone when practicable.
Although limited in application, there may be situations where removal of an object
outside the right of way is appropriate. The possible mitigative measures are listed as
follows in order of preference:
a. Remove
b. Relocate
c. Reduce impact severity (using a breakaway feature)
d. Shield the object by using longitudinal barrier or impact attenuator use
engineering judgment when considering the following objects for mitigation:
e. Wooden poles or posts with cross-sectional areas greater than 16 square inches
that do not have breakaway features.
f. Signs, illumination, cameras, weather stations, and other items mounted on non
breakaway poles, cantilevers, or bridges.
g. Trees with a diameter of 4 inches or more, measured at 6 inches above the
ground surface.
49
h.
Fixed objects extending above the ground surface by more than 4 inches; for
example, boulders, concrete bridge rails, signal/electrical/ITS cabinets, piers, and
retaining walls.
i. Drainage items such as culvert and pipe ends. (40)
e) Trees
When evaluating new plantings or existing trees, consider the maximum allowable
diameter of 4 inches, measured at 6 inches above the ground when the tree has matured.
When removing trees within the Design Clear Zone, complete removal of stumps is
preferred. However, to avoid significant disturbance of the roadside vegetation, larger
stumps may be mitigated by grinding or cutting them flush to the ground and grading
around them.
Removal of trees may be beneficial to reduce the impacts of driving errors, which result
in angle crashes and roadside and clear zone encroachments. It is recognized that
different facilities have different needs and considerations, and these issues are
considered in any final design. For instance, removal of trees within the Design Clear
Zone may not be desirable in contexts such as within a forest, park, or within a scenic
and recreational highway. In these corridors, analyze collision reports’ contributing
factors to determine whether roadside vegetation is contributing to collisions. If large
vegetation is removed, replace with shrubs or groundcover or consult guidance
contained in established vegetation management plans or corridor plans. (40)
f) Culvert End
Provide a traversable end treatment when the culvert end section or opening is on the
roadway side slope and within the Design Clear Zone. This can be accomplished for
small culverts by beveling the end to match the side slope, with a maximum of 4 inches
extending out of the side slope.
a. Bars might be needed to provide a traversable opening for larger culverts. Place
bars in the plane of the culvert opening.
b. Single cross-culvert opening exceeds 40 inches, measured parallel to the
direction of travel.
c. Multiple cross-culvert openings that exceed 30 inches each, measured parallel to
the direction of travel.
d. Culvert approximately parallel to the roadway that has an opening exceeding 24
inches, measured perpendicular to the direction of travel. (26)
Bars are permitted where they will not significantly affect the stream hydraulics and
where debris drift is minor. Other treatments are extending the culvert to move the end
outside the Design Clear Zone or installing a traffic barrier.
50
g) Sign Post
Whenever possible, locate signs behind existing or planned traffic barrier installations to
eliminate the need for breakaway posts. Place them at least 25 feet from the end of the
barrier terminal and with the sign face behind the barrier. When barrier is not present,
use terrain features to reduce the likelihood of an errant vehicle striking the signposts.
Whenever possible, minor adjustments to the sign location may be made to take
advantage of barrier or terrain features. (40)
Signposts with cross-sectional areas greater than 16 square inches that are within the
Design Clear Zone and not located behind a barrier are to have breakaway features. Sign
bridges and cantilever sign supports are designed for placement outside the Design Clear
Zone or shielded by barrier. (26)
h) Traffic Signal Standards/Posts/Supports
Breakaway signal posts generally are not feasible or desirable. Since these supports are
generally located at intersecting roadways, there is a higher potential for a falling
support to impact vehicles and/or pedestrians. In addition, signal supports that have
overhead masts may be too heavy for a breakaway design to work properly.
Other mitigation, such as installing a traffic barrier, is also very difficult. With vehicles
approaching the support from many different angles, a barrier would have to surround
the support and would be subject to impacts at high angles. Additionally, barrier can
inhibit pedestrian movements. Therefore, barrier is generally not an option. However,
since speeds near signals are generally lower, the potential for a severe impact is
reduced. For these reasons, locate the support as far from the traveled way as possible.
In locations where signals are used for ramp meters, the supports can be made
breakaway. (40)
i) Water
Water with a depth of 2 feet or more and located with a likelihood of encroachment by an errant
vehicle is to be considered for mitigation on a project by project basis. Consider the length of
time traffic is exposed to this feature.
Analyze the potential risk to motorists and the benefits of treating bodies of water
located within the Design Clear Zone. A cost effectiveness analysis that considers the
consequences of doing nothing versus installing a longitudinal barrier can be used to
determine the appropriate treatment. (40)
j) Median
Medians are to be analyzed for the potential of an errant vehicle to cross the median and
encounter oncoming traffic. Median barriers are normally used on limited access,
51
multilane, high-speed, high-volume highways. These highways generally have posted
speeds of 45 mph or higher. Median barrier is not normally placed on collectors or other
state highways that do not have limited access control. Providing access through median
barrier results in openings; therefore, end-treatments are needed.
Provide median barrier on full access control multilane highways with median widths of
50 feet or less and posted speeds of 45 mph or higher. Consider median barrier on
highways with wider medians or lower posted speeds when there is a history of crossmedian collisions.
k) Utility Poles
Since utilities often share the right of way, utility objects such as poles are often located along
the roadside. It is undesirable to install barrier for all of these objects, so mitigation is usually in
the form of relocation (underground or to the edge of the right of way) or delineation. In some
instances where there is a history of impacts with poles and relocation is not possible, a
breakaway design might be appropriate. Evaluate roadway geometry and crash history as an aid
in determining locations that exhibit the greatest need.
l) Markings and Signs
To reduce the confusions on the route the following improvements should be
implemented:
a. Worn signs should be renewed
b. Warning signs should be installed at required sections of the route (e.g. before
dangerous horizontal curves, approaching area of intersections, overtaking
prohibited sections, work zones, bridge abutments etc.)
c. Existing markings which cause confusion on the route should be removed
d. The markings should be renewed by repainting and widening centerlines and
edge lines or re-stripping at nonexistent sections of the route. (40)
m) Barriers
Barriers should be properly installed and placed at required locations. Safety barriers
(guardrails) can be effective in reducing the severity of crashes. Also following
countermeasures should be considered:
a.
b.
c.
d.
e.
Extend guardrails at bridge parapets
Guardrails on the bridge should be renewed
Install guardrails at all steeper side slope areas
Deformity guardrails should be renewed or repaired
Missing guardrail sections should be completed. (40)
52
3.7 Safety auditing reporting
After identifying all potential safety issues, the audit report should be prepared. The
outcome of an audit should be a written report, which contains a list of concerns about
road safety matters and recommendations on how these identified potential safety
problems in the existing road will be addressed.
The report should clearly and succinctly identify the process, issues and
recommendations. It is important to note that the recommendations should focus on
safety issues, rather than specify the details of a solution. Also the photographs should
be included in to the report to help readers visualize the problems. Also while writing a
report the video and photographs help to make certain decisions about the safety
problems and good level of recommendations. (37)
3.8 Safety Audit Discussions
After safety audit reporting, a meeting is follow-up to provide an opportunity to discuss
the findings of road safety audit. Discussion can be made between the auditor(s), a
representative from region municipality in which the audit process implemented for and
a representative from National Road Service Commission.
At this discussion/meeting the documentation of the safety actions and project scope
including programming and scheduling are recommended. If there is uncertainty about
the existence of a safety problem exists or about the most appropriate corrective action
to improve the situation, it is desirable to consult with qualified highway and safety
engineer.
The follow up process is lead by the designer/project manager. The designer/project
manager reviews the audit report and prepares a written response to each concern cited.
Each remedial measure suggested in the audit report can be accepted or rejected.
For each accepted suggestion, logical remedial measures should be identified and
adopted by the designer/project manager. The redesign should then advance to diminish
the safety hazard. All project redesigns should be submitted to the audit team for
consideration or re-auditing. The designer/project manager must make sure that
modifications are made to the project which results from agreed improvements described
in the audit report. (20)
3.9 Evaluation of Improvement Projects
Techniques available used by management in evaluating highway projects in terms of
project costs and safety impacts can be grouped into two broad categories.
53
1- Using the first approach, the safety impact is represented by the monetary amount of
accident cost savings called Benefit-Cost Analysis,
2- The second approach considers the cost per expected number of accidents reduced as
the measure of safety effectiveness called Cost-Effectiveness Analysis. (20)
The basic difference between the two categories is the method of measurement of safety
impact.
Benefit = (Accident Cost without Improvement) - (Accident Cost with Improvement)
BCR= Benefits / Cost
Cost effectiveness= Total Cost / Expected Number of Accidents Reduced
54
CHAPTER 4
4 ANALYSIS AND CASE STUDY PRESENTATIONS
4.1 General
The concept of road safety audits (RSA) is relatively new in Nigeria, it can be stated
that (RSA) has never been applied before on Nigerian highways at both the plan stage of
the projects and on existing roads yet.
The Case Study of this thesis is an application of a RSA on a 50 kilometer road section
of Kano – Kaduna express way in Nigeria starting from Kano state. The case study road
is a four lane divided highway with a lane width of 3.3 meters, with a varying shoulder
widths from two and half meters to zero meters.
At some places, concrete median barrier height of 1.2 meters has been used. The case
study road is one of the three major four lanes divided highways in Nigeria which
connects almost all cities of northern Nigeria with Abuja that is the federal capital city of
Nigeria with many markets and big towns along the road.
THREE MAJOR HIGHWAYS
Figure 4.1 Map of Nıgeria Showing Three Major Highways. (44)
55
A
AUDIT START STATION
B
AUDIT END STATION
Figure 4.2 Map Showing Kano-Kaduna Highway (44)
The objective of the case study can be explained as follows;
a. Carry out road safety audit along 50 km section of Kano-Kaduna highway.
b. Identify potential safety problems for road users.
c. Carry out RSA along selected section of the highway to identify typical recurring
problems.
4.2 Preconditions
4.2.1 General Project Data
a) Function of the Road
The existing paved road was constructed in the year 1986 in order to improve the
accessibility of almost all northern cities in Nigeria with newly created federal capital
city of Nigeria Abuja.
It also serves as major highway connecting northern Nigeria with its southern
counterpart. The route is also an important arterial which connects cities from north-west
of Nigeria like Sokoto, Zamfara, Katsina and cities from north-east like Maiduguri,
Yobe, Adamawa with those on the north central such as Kaduna and capital city Abuja.
All of these cities are connected by the help of this route. The route is a federal road and
the main function is to facilitate regional distribution of traffic (intercity movement).
The audit route has a length of 219 km from Kano to Kaduna in which 50 km section
was selected as a case study. The audit section of the road is surrounded by many
commercial and agricultural activities along the roads with several markets.
56
These serve for peoples from northern part of Nigeria who brings their agricultural
products and sell to those from the southern part. They used the same route to convey
their products to all regions of Nigeria.
b) Traffic Volumes
Hourly traffic volume counts were conducted along the audit case study road at station
km 12+000 for two different periods of a day that is in the morning and afternoon
sessions for the two different directions of the highway and the result obtained for the
hourly volume count were used to compute an Average Annual Daily Traffic (AADT)
for the road section using some conversion factors for determining AADT.
The average annual daily traffic of the road was found to be 7465 vehicles/hour (2013).
c) Accident Data
The table below shows the summary of accident data of Nigeria for the period from
1990 to 2001
Table 4.1 Accident Data of Nigeria (41)
Years
Total Cases Reported
Persons Killed
Persons Injured
1990
21721
8154
23687
1991
27498
9525
22686
1992
22909
9620
24508
1993
21412
9454
25759
1994
18218
7420
24416
1995
17000
6647
17938
1996
16793
6364
14554
1997
9034
3616
15290
1998
16046
6538
10786
1999
12424
5429
17341
2000
12705
6521
20677
2001
13801
8012
23249
204561
87300
240621
Total
Traffic accident data which were taken from the Police Commands and Federal Road
Safety Corps of Nigeria is shown in table below. There is more specific traffic accidents
data information which will be given in appendices part of the thesis.
Table 4.2 Four Years’ Accident Data for Kano-Kaduna Highway (2)
Kano-Kaduna Highway
Years
Number of Accidents
Persons Killed
Persons Injured
2008
426
302
394
2009
309
274
297
2010
332
273
294
2011
288
242
362
1355
1091
1347
Total
57
d) Road Standards
The audit route can be classified as multilane rural arterial highway (by referring to
AASHTO standard) based on the roadway features observed.
It was constructed in the year 1986 and has been served as four lane divided highway
road. Existing road platform width is 13.2 m. The existing road pavement surface is
surface treatment and generally passing through from flat, rolling and partially
mountainous terrain.
The shoulder of road section is completely unpaved with a width of 2.5 meters at few
places and majority of the road there is no shoulder completely and even the road lane is
deteriorated due to lack of maintenance since initial construction of the road.
e) Speed Limits
The posted legal speed limit of the audit route is 100 km/hr. On the other hand, at some
sections of the route the speed decreased to 50 km/hr which may be due to the presence
of towns and markets very close to the roadway.
During site visit a spot speed observation was carried out and speed of some vehicles
were observed. The observations were around 130 and 160 km/hr respectively which
were all above the legal posted speed limit of the road. At some sections of the road,
vehicles are subjected to move at a speed of less than 20 km/hr due to the presence of
large potholes on the road section.
4.2.2 Surroundings/Land Use
At the beginning of the audit route there are gardens and farm houses where crops and
milk are produced. There are also a lot of industrial plants such as sugar and tomatoes
processing factories along the road.
There are also many educational institutions along the road like Kano State Sport
Institute, Kano State Information Technology Institute and many others. There are also
many markets as a result of industries and farming activities along the audit road. There
are also many petrol stations along the route which are all connected to both side of the
road.
Beginning from 26+450 km section of the road on both sides there are hectares of land
for irrigation farming that is the largest irrigation farming in the whole Nigeria
controlled by Hadejia Jamaare River Basin Development Authority under federal
government of Nigeria.
There are lots of villages and towns along the road their approximate kilometers and
directions are given in table 4.3 below.
58
Table 4.3 Towns Located along the Audit Road
KM
DIRECTION
00+300
01+700
03+800
05+600
08+600
11+500
22+900
31+300
35+200
41+500
45+700
48+900
02+300
13+300
21+500
32+100
38+400
41+700
45+600
Kano-Kaduna
Kano-Kaduna
Kano-Kaduna
Kano-Kaduna
Kano-Kaduna
Both side of the road
Both side of the road
Kano-Kaduna
Both side of the road
Kano-Kaduna
Kano-Kaduna
Both side of the road
Kaduna-Kano
Kaduna-Kano
Kaduna-Kano
Kaduna-Kano
Kaduna-Kano
Kaduna-Kano
Kaduna-Kano
TOWN NAME
Durba
Waratallawa
Fari
Tamburawa
Matage village
Karfi village
Imawa
Bauren Tanko village
Kura local Government
Yadakwari Village
Dorawar Sallau Village
Ciromawa Town
Kadawa Gate Town
Dogon Dabino Village
Dakasoye Village
Samawa Town
Tudun Bayero Village
Fari Town
Dangwuro Village
4.3. Methodology
After the audit route was determined and selected, all necessary information and data
about the route were collected. Before going to the site for observations, some
information was gathered out and checked such as;
a. Route map
b. Accidents information data for the five years
c. Road geometry inventory (lanes width, surface types, shoulder, median width
road
Characteristics)
All of this background information was collected from the relevant authorities. Accident
data was obtained from both Nigerian Police Force and Federal Road Safety Corps of
Nigeria at their offices in Kano and Kaduna States.
After gathering all those information audit surveys on the case study route were started
on the first day from Na’ibawa interchange which selected as a starting point and
marked as 00 + 000 km. Photographs and video records were also made during the site
visit which are used to make final discussions and evaluations.
59
Both sides of the audit route were observed and all safety audit aspect of the road was
recorded on a safety audit checklist. Photos were taken for subsequent comments and
discussions on observed hazards during the field survey.
During the field survey, the following aspects of route were identified;
a. Locations in which shoulder widths are inadequate
b. Markings that are not exist or in a complex condition ( old and new markings
mix each other)
c. Problematic road side zones that include dangerous features which can create
specific danger within the clear zone width. (Trees, Utility Poles, Concrete
Structures)
d. The existence of various kinds of trees and other vegetation which obstruct the
sight distance of the drivers
e. Improper location of the bus stops
f. Non guarded-rail sections
g. Concrete structures and dangerous wall endings
h. Improper information signs
i. Improper junction designs
(10)Improper drainage structures
During observations, the safety audit checklist was filled. Observations along the route
and photos were also illustrated at subsequent paragraphs of the report.
4.5 Observations Performed During Audit
Potential safety problems and hazards were observed along the route during the field
survey for further evaluation. All of the problems and deficiencies were recorded in the
checklist.
Checklist is categorized under two main headings. One of them is road design another
one is the road side area. When conducting the audit, the safety problems were
categorized under these main headings and recorded to the respective part of the
checklist.
The checklist table consists of five columns. The first and second columns of the
checklist define the Kilometer and distance respectively. Kilometer and distance define
the location of hazard and potential safety areas. Third column explains the type of the
hazards which arise from the road design or road side area, the fourth column of the
checklist give the auditor comments and short suggestions to the problems and hazards
and the last column gives a reference of an example picture to show the real hazard in
the appendices section of the thesis.
60
4.4 Hazard List
Table 4.4 Hazard Types
Number
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
Number
18
19
20
21
22
23
24
25
26
27
28
29
30
31
A-ROAD DESIGN
Hazard Name
Shoulder missing
Shoulders too narrow
Shoulder unpaved
Improper junction design
Improper connection to shop, petrol station or other commercial
activities
Improper connection to small access road
Improper connection to roadway
Improper median opening
Limited sight distance
Improper or dangerous pedestrian crossing
Too small radius of horizontal curve
Too small radius length of vertical curve
Speed limit too high
Speed limit too low
Improper vertical sign
Improper horizontal sign
potholes
B-ROAD SIDE AREA
Hazard Name
Dangerous fixed object on the roadway
Dangerous fixed object on road side or median
Dangerous fixed object on road island
Temporary road narrowing (e.g. bridge)
Fixed massive poles near road or in the median(lighting, electricity etc)
Road edge deterioration
Big trees or trees close to the road
Dangerous bridge piers
Dangerous hedge
Dangerous cut form
Dangerous free stones or rocks
Dangerous support for signs(advertisement or road information sign)
House or other building so close to road
Steep edge slope without guardrail
61
Table 4.4 Hazard Types (continuation)
32
33
34
35
36
37
Dangerous guardrail start and end
Improper culvert design on the road side
Improper commercial activities on the roadside
Improper bus stop design
Missing sign
Use of non standard sign
Most of the connection roads observed during the audit were improperly designs. In
almost all the 50 km section of the road observed during the audit, road markings were
completely worn or missing. All the road signs such as warning signs were also
completely worn out and some were improper at some sections of the road.
Moreover, the road pavement was found as not suitable for the design speed. Some
sections of the audit route pavement were patched and these were out of date and
weathered. A lot of potholes were not even patched which could contribute a lot to the
high number of accidents on the road.
It was observed that safety zones were inadequate at some sections and completely
missing in some other parts of the road. The concrete structures, big trees, buildings,
fixed objects were in the road environment. Free stones and rocks, fixed massive
electricity poles were also near to the roadside environment. Drainage structures were
observed as hazardous within the safety zone.
The safety checklist of the route was divided into two ways/directions of observations.
During the site investigation, the hazardous objects within the safety zone were
photographed and reported in detail below.
4.6 Comparison with the Standard
The existing values of cross section elements for the audit road have been measured and
compared with AASHTO Highway Design Manual (Multilane Rural Arterial Highway)
as shown in table 4.5 below.
62
Table 4.5 Comparison with Standard (42)
Number Roadway Element
1
Design speed
12
AASHTO Standard Values
60-120 km/hr Depending on
the terrain
Number of lanes
Four or more
Travel lane width
3.6 m minimum
Right shoulder width 2.4 m
Left shoulder width
1.2-1.8 m
Turn lane width
3.6 m
Median
width Wide median 7.5 m minimum
including
left
shoulders
Roadside clear zone
9m
Fill/Cut slope
4H:1V
Minimum
bridge 6.248 m
vertical clearance
Bridge width
At least full approach traveled
way width or plus 0.6 m
clearance on each side
Control of access
Partial/by regulation
Observed Values
100 km/hr
2
3
4
5
6
7
Four lane
3.3 m
0.0-2.2 m
0.0-1.0 m
0.0
4.0 m
13
Alignment
14
Bus turnouts
15
Pedestrians crossing
8
9
10
11
0.0
5H:9V
4.5 m
2/3 of traveled way
width
Uncontrolled
access
Adequate and smooth flowing Poor alignment
alignment
A well marked widened No widened
shoulder or an independent turn shoulder or
out is highly desirable and independent
should be provided at locations turnout
where there are known
concentration of passengers
Controlled
Uncontrolled
4.7 Safety Audit Checklist of Existing Road
Tables 4.6 and 4.7 below shows the safety audit checklist, with all the field observations
recorded during the site visits for both sides of 50 km section of Kano-Kaduna multilane
rural arterial highway wıth column showing example of the hazard in the appendices
sections as P1, P2, P3 up to P24.
63
SAFETY AUDIT CHECKLIST OF EXISTING ROAD
Date: 17/8/2013
Conducted by: Nura Bala
Weather: sunny, partly cloudy
Kano-Kaduna Direction
KM
DISTANCE TYPE OF
COMMENTS
(M)
HAZARDS
Start station of the audit (Na’ibawa
0
0
interchange).
Dangerous to road users
1
100-400
1
Increases accident potential
2
000
1,4,7
Increases accident risk
2
200
29
Decrease visibility
2
400
19
Decreases roadway capacity
2
300-600
23
Creates danger to motorist
2
500
21
Causes accidents
2
500
7
Increases accidents potential
2
700
7
Increases road side accidents
2
700-900
19
Decreases safety
2
700-800
31
Reduces roadway capacity
2
800-900
23
Causes confusions leading to
2
900
15
accident
Causes an accident
3
100
5
Increases accidents
3
200-300
34
Dangerous to coming vehicles
3
400
5
Decreases roadway capacity
3
400-900
23
Increases road side accidents
3
700-900
19
Decreases roadway capacity
3
800-900
1
Causes accidents
5
000
28
Causes confusion to drivers
5
100
15
Causes danger to pedestrians
5
200
9
Limited sight distance causes
5
200-300
9
accidents
Increases roadside accidents
5
200-800
28
Causes accidents
5
300
5
Decreases road capacity and cause
6
200-700
23
accident
Table 4.6 Safety Audit Checklist for Kano-Kaduna Direction
64
APPENDIX
REFENCE
P1
P9
P9,P24
P6
P4
P9
P16
P24
P24
P13
P10
P9
P20
P7
P17
P7
P9
P4
P9
P20
P23
P23
P7
P9
6
6
6
6
6
6
7
7
7
7
8
8
9
9
9
9
10
10
10
10
11
11
11
12
12
13
13
13
14
14
16
17
400
500-600
600
600
700
800
100
100-300
200-500
400
200-700
700-900
000-100
200
600-700
700-900
000
600-700
800
900
000-200
300-700
400
500
700
000
100-300
300
200
400-900
300
200-600
28
19
15
8
16,4,34
35,23
9,5
1
23
5
31
31
17
7
34
1,7
34
34
5
7
19
23,17
34
35
7
37
19
37
10
17,23
7
9
Causes road side accident
Causes road side accidents
Makes confusion to drivers
Increases accident rates
Mislead drivers
Causes accidents
Increases accidents
Decreases roadway capacity
Decreases capacity of roadway section
Causes accidents
Increases accident risks
Increases road side accidents
Increases accidents on the road
Causes accidents
Increases danger to road users
Reduces roadway capacity
Causes road side accident
Causes accident for vehicles leaving the road
Cause accident with coming vehicles
Contribute to high risk of accidents
Increases danger of roadside accident
Increases accident rates
Causes roadside accident
Causes danger to passengers and motorist
Increases confusions to drivers
Mislead drivers
Danger for roadside accident
Increases confusions to drivers
Causes danger of crossing to pedestrians
Decreases road capacity and causes accidents
Increases collision accidents
forced drivers to reduce speed and cause
accident
Contribute to accidents
19
200-300
17
Decreases roadway capacity
20
300-800
1,23
Increases severity of accident
21
500-700
32
Table 4.6 Safety Audit Checklist for Kano-Kaduna Direction
65
P4
P20
P18
P24,P17
P14,P9
P23,P7
P9
P9
P7
P10
P10
P7
P24
P17
P9,P24
P17
P17
P7
P24
P4
P9
P17
P14
P24
P4
P8
P7
P24
P23
P7
P9
P11
22
22
23
24
24
24
25
Increases roadside accident
700
34
Causes accident with errant vehicles
800-900
1
Causes accidents with passengers
000
35
Causes accidents with passengers
300
35
Increases roadside collision severity
500-680
22
Causes accident with turning vehicles
700
8
Causes accidents
10017
200,800
Causes collision with coming vehicles
28
600
5
Causes collisions with leaving vehicles
29
700
6
Serves as appoint of accident
30
900
4
Increases severity of roadside accidents
32
200-400
34
Allowed errant vehicles to park on the road
34
500-600
1
Causes accidents
34
400
8
Causes accidents
35
700
5
37
000-200
1,23 Decreases roadway capacity
Increases danger of accidents
37
400
35
Causes roadside accident
38
200
19
Increases danger of accidents
38
400-700
24
Causes accidents
39
100-300
17
Increases severity of roadside accidents
40
400-800
31
40
500-600
1,23 Decreases capacity of the road section
Mislead drivers
40
900
15
Increases danger of accidents
41
400
6
Increases roadside accidents severity
42
100-300
24
Causes accidents
42
500
5
Causes accidents for turning vehicles
42
800
8
Dangerous to pedestrians crossing
43
100
10
Danger for vehicles moving at high speed
43
400
14
44
100-400
1,23 Decreases roadway capacity
Causes accidents
44
300
5
Increases accident potential
44
600
29
44
700-900
22,24 Increases severity of roadside accidents
Causes accidents
44
800-900
17
Serves as accidents location
44
900
6
Causes roadside accidents
45
100-200
34
Table 4.6 Safety Audit Checklist for Kano-Kaduna Direction (Continuation)
66
P17
P9
P14
P14
P2
P8
P7
P7
P24
P24
P17
P9
P18
P7
P9
P14
P4
P13
P7
P10
P9
P20
P24
P3
P7
P18
P8
P22
P9
P7
P12
P2
P7
P24
45
45
45
46
46
47
47
47
47
48
48
48
48
49
49
49
49
49
49
200-400
600
800
200-300
600-700
100
200
500-700
800
100-300
500-800
600-900
700
200
400
500-800
600
700
800-900
22
5
15
17
22
8
21
17,31
5
34
24
17
6
4
22
1,17
36
4
22
Causes accidents when vehicles hit
Causes accidents
Causes confusion to drivers
Reduces travelling speed
Increases severity of accidents
Causes accidents with turning vehicles
Causes side collision accident
Causes road side accident
Increases accident risks
Causes road side accident
Increases severity of roadside accident
Causes vehicles to reduce speed
Increases danger of accidents
Increases accidents and delay
Causes roadside accident
Reduces roadway capacity
Causes confusion to drivers
Causes accidents and delay
Causes accident to uncontrolled vehicle
P2
P7
P20
P7
P2
P18
P16
P10
P7
P17
P13
P7
P24
P24
P2
P7
P24
P24
P2
Table 4.7 Safety Audit Checklist (Continuation) For Kano-Kaduna Direction
P1, P2, P3 up to P24 implies picture one, picture 2, picture 3 up to picture 24 which
indicates a picture showing an example of the hazard in the appendices section of the
thesis.
67
SAFETY AUDIT CHECKLIST OF EXISTING ROAD
Date: 02/9/2013
Conducted by: Nura Bala
Weather: sunny, partly cloudy
Kaduna-Kano direction
KM
DISTANCE TYPE OF
COMMENTS
(M)
HAZARDS
Increases danger of roadside
1
100-500
22
accident
Causes accidents
2
100
5
Increases danger of accidents along
2
200-350
34
roadside
Causes accidents with pedestrians
2
400
10
Reduces roadway capacity
2
400-500
23
Increases severity of accident
2
700
19
Causes roadside accident
2
800
29
Reduces roadway capacity
2
800-900
1,23
Decreases roadway capacity
3
100-300
1
Causes roadside accidents
3
400
19
Reduces roadway capacity
3
500-900
23
Reduces travel speed
4
200
17
Reduces travel speed
4
300-400
17
Causes danger of roadside accidents
4
400-600
31
Danger of accident with passengers
4
800
35
Causes danger of accidents
4
800-900
34
Increases danger to coming vehicles
5
600
5
Increases severity of roadside
5
700-800
31
accident
Danger for motorist
5
800
11
Dangerous to motorist
5
800
9
Causes confusion to drivers
6
600
15
Causes danger of accidents
6
900
5
Increases accidents potential
8
300
14
Causes danger of accidents
8
400
5
Causes accidents
9
500
5
Causes confusion to drivers
10
700
15
Causes accident
11
300
29
Causes roadside accident
12
400
19
Risk of accident
13
500
15
Reduces travel speed
13
600-700
17
Table 4.7 Safety Audit Checklist for Kaduna-Kano Direction
68
APPENDIX
REFENCE
P2
P7
P17
P8
P9
P4
P12
P9
P9
P4
P9
P7
P7
P10
P14
P17
P7
P10
P23
P23
P20
P7
P22
P7
P7
P20
P12
P4
P20
P7
Improper connection to small access road
13
900
6
Causes confusion to drivers
14
300
36
Increases accident risks
15
800
6
Causes roadside accident
16
000
30
Increases severity of roadside accidents
16
500-700
24
Causes accidents
18
100
29
24
600
10
Causes danger of crossing to pedestrians
24
800-900
34
Causes accident with out of controlled vehicle
26
300-400
22
Increases severity of roadside accidents
26
600-700
34
Increases accident risks
26
800-900
31
Causes roadside accident
27
300
15
Causes confusion to drivers
27
800
25
Increases accident risks
29
200-400
31
Increases severity of roadside accident
29
700
32
Dangerous guard rail start
30
100
4
Causes accidents and delay
32
200
14
Lower speed limits increases accident risks
32
500
4
Causes accidents and delay
35
300
29
Causes roadside accident
37
800
21
Causes danger to approaching vehicles
37
900
7
Causes accidents
38
200-600
24
Increases severity of roadside accidents
38
700-900
30
Causes roadside accident
39
400-500
34
Causes accidents with out of controlled vehicles
40
100-600
23,1 Reduces roadway capacity
41
300
10
Dangerous to pedestrians crossing
41
800
5
Causes accidents
43
500-800
22
Causes roadside accident
43
600
8
Causes accidents with turning vehicles
43
900
29
Causes confusion to drivers
44
300
8
Dangerous for turning vehicles
44
500-700
1
Causes errant vehicles to park on the travel lane
44
800
35
Dangerous for pedestrians
44
900
4
Causes accidents and delays
45
100-600
1,23 Reduces roadway capacity
46
100-700
1,23 Reduces roadway capacity
46
500
15
Causes confusions to drivers
Table 4.7 safety audit checklist (continuation) for Kaduna-Kano direction
69
P24
P24
P24
P15
P13
P12
P8
P17
P2
P17
P10
P20
P20
P10
P11
P24
P22
P24
P12
P16
P24
P13
P15
P17
P9
P8
P7
P2
P18
P12
P18
P9
P14
P24
P9
P9
P20
47
47
47
48
48
48
48
48
49
49
200-700
300
600-900
100
100-600
200
500
700
200
800
19
35
34
6
1
29
4
10
36
8
Causes roadside accident
Dangerous to passengers
Causes roadside accident
Causes accidents
Allowed vehicles to park on the travel lane
Causes confusion to drivers
Causes accidents and delays
Causes danger of crossing to pedestrians
Causes confusions
Danger of accidents to turning vehicles
P4
P14
P17
P24
P9
P12
P24
P8
P24
P18
Table 4.7 safety audit checklist (continuation) for Kaduna-Kano direction
P1, P2, P3 up to P24 implies picture one, picture 2, picture 3 up to picture 24 which
indicates a picture showing an example of the hazard in the appendices section of the
thesis.
4.8 Typical Hazards
a) Utility Poles in the Safety Zone
Utility pole can cause severe roadside crashes. Along the audit route there have been
mostly electricity poles that are made of concrete and telephone poles that are made by
wood. They are all located within the safety zone area on both sides of the route.
Because of the poles are located in the safety zone area, they create high potential safety
risks for road users.
Along the audit route the most noticeable pole type is electricity poles which are made
of concrete. The electricity poles have been located within the safety zone at most
places. These locations have been assessed as potential dangerous points in which
severity of crashes were increased after loss of control accidents. (Figure 1.4)
70
Figure 4.3 Dangerous Electric Poles Close To the Road (Km 47+200)
b) Trees in the Safety Zone
This section addresses crashes involving trees. Along the audit route trees can be
thought as a potential danger for road safety. There are lots of trees with varying size
and type along the audit route both on the roadside within the safety zone and also on the
road median. Some of the trees have diameter greater than one meter. During the field
survey, the trees which involve the high potential safety risk were recorded. Most of the
trees that have been on the route can be considered as fixed objects.
Some of the trees have been lined at the beginning section of the route and all of the
trees are within the safety zone area. Between km 03+700 and km 05+800 trees have
been so close to the road. Between km 11+000 and 17+200, the sight distance have been
prevented by trees. At some stations such as station km 46+600; the trees have been
located on the road median which creates danger to the drivers. At some sections of the
route, the shoulders have been covered by small trees and vegetations.
71
Figure 4.4 Dangerous Trees within the Safety Zone Area (Km 13+100)
c) Improper Signing and Marking
Most of the information signs have been located at inappropriate locations and are not in
accordance with the standard, At km 40+900, the sign has been almost covered by
vegetation and it is too short which cannot permit drivers to see it before reaching the
sign. It was also observed that all the markings on both sides of the route have been
completely worn out to the extent that drivers cannot even see any indication. As a result
of that drivers use the road with no marking condition in which might contribute to high
number of accidents along the route.
Figure 4.5 Worn Out Sign (Km 5+300)
72
d) Improper Access Management
There have been many gasoline stations along the audit road located at short intervals
and almost all the gasoline stations observed within the 50 km audit section have been
improperly connected to the main road.
There has been a gasoline station at station km 46+600. The entrance and exit sections
of the petrol station have been too close to the road in which a driver coming out from
the gas station cannot clearly see the vehicles coming from the main road travelling at
very high speed. In addition to that, concrete wall endings and information signboard of
the petrol station create high hazardous risk for road users. There have also been trees on
the roadside just near the entrances which limited the sight distance for coming vehicles
from the roadway.
Figure 4.6 Improper Connection to Gas Station (Km 3+400)
e) Improper Pedestrian Crossings
A pedestrian crossing or crosswalk is a designated point on a road at which some means
are introduced to assist pedestrians wishing to safely cross the road. They are designed
to keep pedestrians together where they can be seen by motorist, and where they can
cross most safely across the flow of vehicular traffic.
As observed and recorded during the audit survey, there have been many uncontrolled
pedestrians crossing on the road. At km5+200 and km24+600 there have been vertical
signs indicating the pedestrian crossing, but on the road way there have been no any
facility for pedestrians to cross the roadway safely.
73
Figure 4.7 Improper Pedestrian Crossings (Km 5+200)
f) Improper Shoulder Widths and Danger of Edge Deterioration
The shoulders observed on both sides of the road during the audit survey have been
generally all unpaved. There have been some other sections in which shoulders are
completely missing. There has been no exact width of the shoulder throughout of the
roadway. It varies from 0.00 m to 2.00 m; it was observed that shoulders have only been
available in few places of the road that were renovated recently.
Apart from missing and inadequate shoulders on the road; there has also been another
serious problem of edge deterioration at majority of the roadway parts. It can cause a
serious safety problem along the road as it affects the normal 3.2 m lane width of the
road lane. Some parts of the missing shoulder where edge is deteriorated even vegetation
covers the edges of road lane.
74
Figure 4.8 Shoulder Missing (Km 44+100)
g) Improper Fill Slope Designs
At both sides of the audit route there are many sections where the side slopes are steeper
than the desirable. Federal Ministry of Works which is responsible for all federal
highways in Nigeria uses AASHTO standards. AASHTO considers side slopes of
4H:1V to be the steepest slopes for permitting safe vehicle controls.
As measured during the audit some sections of the route, fill slopes of 5H:9V, 7H:12V,
4H:5V have been used. At station km 02+800 and km 08+700, and also between km
40+400 and 40+700; there have been very high steep side slopes. If an errant vehicle
leaves the highway at these locations, the severity of the collision can be increased
considerably.
Figure 4.9 Dangerous Fill Slope (Km 2+700)
75
h) Improper Guardrails
Along the audit route there have been many improper designed or improper positioned
guardrails together with their improper starting and terminations which become a great
roadside hazard. Between station km 21+500 and km 21+700 there have been many
dangerous gaps on the guardrail arrangements. For loss of control accidents, these
missing guardrails can create a great danger.
Figure 4.10 Dangerous Guardrail Section (Km 21+500)
i) Pavement Problems/Potholes
Within the area studied, the condition of pavement varies. Generally, road surfaces
appear to be roughest in many old sections with cracks, bumps and potholes on them.
The pavement conditions have been particularly poor.
There has been considerable rutting those results in pounding of water on the roadway.
There is also considerable deterioration at pavement edges. There have been many
patches on the road surface. Because of this situation, at some sections road surface has
been rugged.
At some sections, the road surface was collapsed because of the probable improper
pavement design and construction. It was recorded that the condition of the road surface
has been noticed as “poor” throughout the section as observed during the audit.
76
Figure 4.11 Dangerous Potholes on the Pavement (Km 9+00)
j) Improper Placement of Vertical Signs
Along the route, there have been many improperly placed vertical signs. Almost all the
vertical signs along the audit were all located within safety zone area which creates a
potential safety hazard to motorist. At many sections of the route observed vertical signs
can be one of the greatest hazards causing accidents.
Figure 4.12 Improper Placements of Vertical Sign within the Safety Zone (Km 6+400)
77
K) Improper Market Location and Commercial Activities
During the audit survey it was noticed that there have been many locations on both side
of the road in which small markets and many other commercial activities were located.
They can create a great hazard to vehicles using the road some locations observed have
been very close to the road side (within the safety zone area) on the other hand, some of
the commercial activities have occupied area even on the shoulder of the road.
At km between 3+200 and km 3+300 there have been market and bus stop location for
travelling far distance from Kano. As a result the place attracts many peoples and causes
all passing vehicles to reduce their speed as lower as 10 km/hr. The location has been
recorded as one of the locations in which many accidents were happened.
Figure 4.13 Dangerous Tress, Signboard And Objects Close to the Roadway (Km
3+200)
l) Houses and Concrete Structures in the Safety Zone
Houses and concrete structures located in critical positions or within the safety zone
create a great danger for all vehicles using the road. Along the road it was observed that
there have been many locations in which house and structures made of concrete were
located very close to the roadway.
One of the most hazardous sections of the audit route has been mentioned between km
16+000 and km 16+100. There have been houses located very close to the road within
the safety zone as shown in the figure below. There are also many concrete foundations
for vertical signs within the safety zone.
78
Figure 4.14 Dangerous Concrete for Support Close To the Road (43+200)
m) Road Narrowing
Road narrowing is also one of the hazards recorded on the road during the safety audit
survey. At station km 00+100 the road narrows and changes from three lanes to two
lanes as a result of bridge a head; these can increase accident risk to vehicles
approaching the bridge.
A narrow bridge makes it difficult for drivers to safely maneuver in emergency and nonemergency situations because there is simply no enough space to maneuver. Narrow
bridges are particularly hazardous and collisions with bridge ends are relatively
infrequent but they are often severe.
Figure 4.15 Dangerous Road Narrowing (Km 0+300)
79
n) Missing Safety Zone
A Clear Zone is an unobstructed, traversable roadside area that allows a driver to stop
safely, or regain for control of a vehicle that has left the roadway. By creating clear
zones, roadway agencies can increase the likelihood that a roadway departure results in
a safe recovery rather than a crash, and mitigate the severity of crashes that do occur.
At the case study road, the width of the safety zone is zero at majority of the roadway
and maximum of five meters at few places which is not sufficient and not in accordance
with the standards.
Figure 4.16 Missing Safety Zone (Km 5+900)
4.9 Proposal of Countermeasures
After all the above data were collected and analyses, some counter measures for some
typical hazards were proposed as follows;
a) Utility Poles
At km 24+500 and km 47+200 and many other sections on the route surveyed, there are
electric poles within the safety zone area, which are made of concrete. There are some
applicable countermeasures to be applied to such situations to minimize accidents
severity as follows.
1- The first one is to install reflector on the poles, which can be seen by drivers from far
distance. This solution has low cost and short term implementation.
2- The second is to install guard rail or crash cushion for hazardous utility poles near
curve locations, which has low/mid cost of implementation.
80
3- Another one is, removing or relocating utility poles from safety zone area, and it has
the long term and mid/high cost implementation. In addition to this the poles cable can
be buried underground this is also long term and mid/high cost implementation.
b) Trees
At km 16+500 and km 38+700 trees were located within both the safety zone and
median area which creates a great hazard to vehicles. To mitigate the effect of trees
along the route, it may be considered appropriate to remove a tree which clearly presents
an unacceptable hazard to vehicles or to erect a longitudinal barrier, to reduce the risk of
a vehicle striking the tree.
To prevent the stopping sight distance problem, the trees must be removed from safety
zone. However, the potential benefits of removing such obstacles should be weighed
against the adverse environmental and aesthetic effects of their removal. Therefore, trees
should be removed only when considered essential for safety and alternatively, trees
which cannot be removed should be protected by guardrails.
Removal of trees within the Design Clear Zone may not be desirable in places such as
within a forest, park, or within a scenic and recreational highway. In such cases,
collision contributing factors report is analyzed to determine whether roadside
vegetation is contributing to collisions. If large vegetation is removed, replace with
shrubs or groundcover or consult guidance contained in established vegetation
management plans or corridor plans.
c) Safety Zone Area
At almost all the road section inspected, there is no clear road side zone which is a
serious hazard to vehicles. The importance of a clear zone is to provide as much clear,
traversable area for a vehicle to recover as practicable given the function of the roadway
and the potential tradeoffs.
Elements such as side slopes, fixed objects, and water are features that a vehicle might
encounter within the safety zone when it leaves the roadway. These features present
varying degrees of deceleration to the vehicle and its occupants. The measures to
mitigate these depend on the probability of a collision occurring, the likely severity, and
the available resources.
The measures for mitigation of these hazards are listed below in order of priority as
follows:
(1) Removal
(2) Relocation
(3) Reduction of impact severity (using breakaway features or making it
raversable)
(4) Shielding with a traffic barrier.
81
d) Markings and Signs
At many locations on the road inspected, there are many signs confusing drivers on what
decision to be taken and in some locations, the signs were either worn-out or completely
missing. To reduce the confusions on the route the following improvements or
countermeasures should be considered:
a. Worn signs should be renewed
b. Warning signs should be installed at required sections of the route (e.g. before
dangerous horizontal curves, approaching area of intersections, overtaking
prohibited sections, work zones, bridge abutments etc.)
c. Existing markings which cause confusion on the route should be removed
d. The markings should be renewed by repainting and widening centerlines and
edge lines or re-stripping at nonexistent sections of the route
e. Markings/signs should be placed where missing.
e) Shoulders
At majority sections of the roadway inspected, the shoulders are either inadequate or
completely missing. A shoulder provides space for emergency stop or for errant vehicles
to park, without shoulders vehicles should be parked on the roadway which increases
chances for accidents. In such situations the countermeasures to be employed are as
follows:
a. Shoulders should be constructed where missing
b. Shoulders should be paved
c. Shoulders should be wide/adequate
d. Upgrading and re-surfacing of shoulders should also be considered.
f) Houses and Concrete Structures
At km 38+700 and km 43+ 200 there is house and concrete structure within the safety
zone, the appropriate possible counter measures to be applied to that locations are either
removing or relocating from the safety zone. Also installing the guardrails or barriers
along the building section can be a possible solution for reducing the accident risk.
g) Bus Stops
Along the audit route all of the bus stops should be relocated. Also bus stops should be
visible for all road users. Beside this bus stop signs should be installed properly.
Moreover the construction of the bus bays should be considered as another possible
solution.
h) Barriers
Barriers should be properly installed and placed at required locations such as Km
21+500. Safety barriers (guardrails) can be effective in reducing the severity of crashes.
Also following countermeasures should be considered:
82
a. Extend guardrails at bridge parapets
b. Guardrails on the bridge should be renewed
c. Install guardrails at all steeper side slope areas
d. Deformity guardrails should be renewed or repaired
e. Missing guardrail sections should be completed
h) Entrance to the Road Side Facilities
Almost all the entrances of the Gas Station along the road section surveyed should be redesigned in a way not to include any hazard risks. Widening the shoulders and traffic
lanes can be a solution.
At Km 3+400 and Km 21+500 along the road section, entrance and exit parts can be
considered highly potentially accident area. Construction of turning lanes at entrance
and exit parts for the vehicles that are coming from both directions can be an alternative
to minimize accident risks. In addition to this there should be warning signs both sides
of the route.
i) Fill Slope
At the fill sides along the roadway surveyed, generally the side slope are steeper than
4H:1V. Slopes steeper than 4H:1V are critical because the possibility of the vehicle to
rollover increases substantially. Fill slopes steeper than 3H:1V should be used with
appropriate safety barriers.
4.10 Case Study Conclusıons
a) After audit survey and analysis it is recognized that the most common hazards
observed are fixed massive objects within the safety zone area, deficient guardrails,
pavement damages, missing shoulders, non-gentle slope and improper bus stop locations
b) Also after comparison of the existing roadway cross section elements with that in
AASHTO standard it is observed that majority of the roadway elements were not in
accordance with AASHTO which is used as Nigerian standard for highway design.
c) Among all the most common hazards recorded during the survey it is observed that
the most dangerous hazards are pavement damages like potholes on the roadway and
pavement edge deterioration, fixed massive objects associated with road side area such
as fixed massive poles and sign post that were improperly placed within the safety zone
area and missing or narrow shoulder along the whole section of the roadway. All these
hazards listed above contributes to the increasing number and severity of accidents
along the road as some accidents were seen physically during the field survey involvıng
fixed massive objects on the road side and some accidents associated with pavement
damages.
83
d) Lack of adequate and proper record of accident data that covers some aspects like
accident location, time of occurrence, type of vehicles involved, reasons or accident
contributing factors, result of collision and many others by relevant authorities in
Nigeria hinders or limits the possibility of this research to analyses the accident data and
understand that either this hazards are among the accident contributing factors on this
road section or not and also to know the level of contribution by each hazard on the
accidents.
e) As observed during the site visit missing and narrow shoulders forces errant and
vehicles that stop for emergency to park along the road section which also has
ınsufficient lane width. Considering the supportive characteristic of the shoulders and
their usability in emergency situations, it can be concluded that most of the present
shoulders might have adverse effect to road safety.
f) Another problem which is not as dangerous as the ones listed above is improper
connection of gas stations and other roadways to the main road which creates additional
danger to the overall safety of the road and its environment.
g) Another significant safety problem is recorded as steep fill slopes. It is considered
that slopes were not designed regarding safety standards on the fill cross sections.
Guardrail application can be considered as a solution for this problem.
h) As discussed above most of the dangerous problems observed on the road section
were associated with road side area, therefore it can be concluded that providing a
cleared and unobstructed road side area will solve larger portion of the accident
problems.
The tables below shows the most common and most dangerous hazards observed during
the site visits for both directions of the road.
84
Table 4.8 most common and dangerous hazards observed
KANO-KADUNA DIRECTION
KILOMETER
MOST COMMON AND DANGEROUS HAZARDS
OBSERVED
00-05
05-10
10-15
15-20
20-25
25-30
30-35
35-40
40-45
45-50
Dangerous fixed object on road side, missing shoulder and
improper junction design
Missing shoulder, potholes, improper commercial activities and
improper bus stop location
Potholes and dangerous fixed objects
Limited sight distance improper trees on road sıde
Missing shoulder and improper bus stop location
Potholes and improper connection to petrol station
Missing shoulder, improper median opening and improper
commercial activities
Potholes and bıg trees close to the roadway
Missing shoulder and improper commercial activities
Potholes and edge deterioration
KADUNA-KANO DIRECTION
KILOMETER
MOST COMMON AND DANGEROUS HAZARDS
OBSERVED
00-05
05-10
10-15
15-20
20-25
25-30
30-35
35-40
40-45
45-50
Dangerous fıll slope and fıxed massive poles close to the
roadway
Missing signs, pavement damages and improper connectıon to
petrol stations
Potholes and dangerous supports for advertisement signs
Dangerous trees on the median and missing shoulder
Fixed massive poles and ımproper commercial activities
Dangerous fill slope and fixed massive poles close to the
roadway
Improper junctıon design and pavement damages
Improper median opening and junction design
Missing shoulder and improper connectıon to petrol statıon
Dangerous trees and fixed massıve objects very close to the
roadway
85
CHAPTER FIVE
5 CONCLUSIONS AND RECOMENDATIONS
5.1 Conclusions
A roadway safety is one of the items that are being brought to the forefront of the
transportation industry. Road Safety Audit (RSA) is becoming a major tool for assessing
the risk on existing roadways. RSA is proactive in nature and look to find safety risk
before crashes occur. It has been used to improve the ability of decision makers’ to
assess risk on the roadways. On the other hand, transportation professionals need such a
tool that can look at the complexity of the roadways.
In this thesis the real practices of road safety audit on existing roads in different
countries were summarized. By taking account these different opinions and auditing
procedures into account a case study has been performed for road safety auditing on
existing road on Nigerian highway. The conclusions that are drawn from the thesis study
can be summarized as follows:
a. Some safety defects observed during the audit study that can be considered as
typical for Nigerian rural highway network can be mentioned as follows:
- Guardrails are deficient or not in appropriate positions,
- Slopes are steep and cannot be considered as gentle regarding road safety,
- Pavement damages such as potholes and pavement edge deterioration are
considerably remarkable,
- Shoulders are insufficient, narrow and are not paved at most locations
b. The realization of safety audits on existing roads bring great support and
guidance for building road safety and improving existing or potential accident
prone locations. With the performed case study and the evaluated results, it is
hoped that it will contribute to the development of ‘safety audit concept’ in
Nigeria.
c. Lack of long term and dependable local accident and countermeasure data
limited the process of this study and these limitations forced the study to make
reasonable acceptations.
86
d. Lack of adequate and proper record of accident data that covers some aspects
like accident location, time of occurrence, type of vehicles involved, reasons or
accident contributing factors, result of collision and many others by relevant
authorities in Nigeria hinders or limits the possibility of this research to analyses
the accident data and understand that either this hazards are among the accident
contributing factors on this road section or not and also to know the level of
contribution by each hazard on the accidents.
5.2 Recommendations
The following recommendations can be drawn from the case study:
a. The case study methodology as a safety audit should be followed and
implemented on all present rural highway networks in Nigeria and all other
roadways for evaluating the overall safety of the country roads.
b. Road safety audit surveys should be done for short intervals to observe changes
in the road structure and equipment as well as the road environment.
c. Road Safety Audits are being considered as more and more important and widely
used tools/applications to increase the road and the road environment safety.
It is necessary to introduce course programs to teach young highway engineers in
all parts of Nigeria and world in general, about these techniques as quickly as
possible. The different teaching techniques such as distant learning and distant
workshop facilities should be applied.
d. Problems with the lack of dependable traffic and accident common database in
Nigeria have adversely influenced the road safety activities. Thus, implementing
reliable and well-designed traffic safety database including road and traffic
statistics and records should be accepted as the first priority action in the recent
future. This common database should be open to researchers with no restrictions.
e. Nigeria should start to invest in the researches of accident reduction factors for
different road safety countermeasures that are currently not available but adapted
from international studies. These researches require long-term studies and should
be implemented as soon as possible.
87
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APPENDIX
Safety Audit Checklist
The Hazards of the route which observed and recorded during the field survey is given
with their appropriate locations on the road.
91
Picture one (P1) Start station of the audit
Picture 2 (P2) Dangerous electric poles close to the roadway km 47+200
92
Picture 3 (P3) Dangerous trees within the safety zone area km 16+500
Picture 4 (P4) Dangerous trees on the road median km 38+700
93
Picture 5 (P5) Warn out vertical sign km 10+700
Picture 6 (P6) Improper placements of vertical sign km 23+200
94
Picture 7 (P7) Improper connection to petrol station km 21+500
Picture 8 (P8) Improper pedestrian crossing km 41+300
95
Picture 9 (P9) Missing shoulder and edge deterioration km 40+100
Picture 10 (P10) Dangerous fill slope km 4+400
96
Picture 11 (P11) Dangerous guardrail section km 21+500
Picture 12 (P12) Dangerous support for advertisement km 32+700
97
Picture 13 (P13) Dangerous tree and objects close to the road km 17+600
Picture 14 (P14) Improper bus stop location close to the road km 6+800
98
Picture 15 (P15) Dangerous house within the safety zone km 38+700
Picture 16 (P16) Dangerous road narrowing km 0+300
99
Picture 17 (P17) Missing safety zone km 15+600
Picture 18 (P18) Improper median opening km 23+300
100
Picture 19 (P19) Dangerous guardrail start km 49+100
Picture 20 (P20) Improper placement vertical sign km 30+500
101
Picture 21 (P21) Confused warning sign km 41+700
Picture 22 (P22) Speed limit too low km 28+600
102
Picture 23 (P23) Limited sight distance km 16+200
Picture 24 (P24) Improper junction design km 24+900
103
104